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Research on effort and motivation commonly assesses how the sympathetic branch of the autonomic nervous system affects the cardiovascular system. The cardiac pre-ejection period (PEP), assessed via impedance cardiography, is a common outcome, but assessing PEP requires identifying subtle points on cardiac waveforms. The present research examined the psychometric value of the RZ interval (RZ), which has recently been proposed as an indicator of sympathetic activity, for effort research. Also known as the initial systolic time interval (ISTI), RZ is the time (in ms) between the ECG R peak and the dZ/dt Z peak. Unlike PEP, RZ involves salient waveform points that are easily and reliably identified. Data from two experiments evaluated the suitability of RZ for effort paradigms and compared it to a popular automated PEP method. In Studies 1 (n = 89) and 2 (n = 71), participants completed a standard appetitive task in which each correct response earned a small amount of cash. As expected, incentives significantly affected PEP and RZ in both experiments. PEP and RZ were highly correlated (all rs ≥ 0.89), and RZ consistently yielded a larger effect size than PEP. In Study 3, a quantitative synthesis of the experiments indicated that the effect size of RZ's response to incentives (Hedges's g = 0.432 [0.310, 0.554]) was roughly 15% larger than PEP's effect size (g = 0.376 [0.256, 0.496]). RZ thus appears promising for future research on sympathetic aspects of effort-related cardiac activity.

Introduction: Several handheld thumb ECG devices for on-demand recording of heart rhythm have become available lately. These can be used both by health-care providers and purchased by laypersons for private use.Area covered: This profile describes the Coala Heart Monitor. This device differs from other handheld ECG monitors in three aspects: 1) it records both thumb and chest ECGs, 2) it uses both RR-dispersion and P-wave morphology for detecting atrial fibrillation, and 3) in synchronization with the chest ECG, it also records heart sounds presented as a phonocardiogram making measurement of systolic time intervals possible. The sensitivity and specificity for detecting atrial fibrillation are high. The use of systolic time interval in patients with heart failure has so far not been evaluated.Expert opinion: The increasing use of long-term prescribed and privately owned handheld ECG devices for on-demand recording of heart rhythm will most probably cause a paradigm shift in arrhythmia diagnostics. Coala Heart Monitor´s use of both chest and thumb recordings as well as analyzing both RR-dispersion and P-wave morphology may offer an advantage in diagnosing atrial fibrillation.

What is the central question of this study? First, we validated easy-to-use oscillometric left ventricular ejection time (LVET) against echocardiographic LVET. Second, we investigated progression of left ventricular ejection time index (LVETI), pre-ejection period index (PEPI), total electromechanical systole index (QS2I) and PEP/LVET ratio during 60 days of head-down tilt (HDT). What is the main finding and its importance? The LVETSystolic time intervals that are easy to detect might be used as parameters reflecting cardiovascular deconditioning. We compared left ventricular ejection time (LVET) measured via ultrasound Doppler on the left ventricular outflow tract with oscillometrically measured LVET, measured at the brachialis. Furthermore, we assessed the progression of the left ventricular ejection time index (LVETI), the pre-ejection period index (PEPI), the Weissler index (PEP/LVET) and the total electromechanical systole index (QS2I) during prolonged strict head-down tilt (HDT) bed rest, including 16 male and eight female subjects. Simultaneous oscillometric and echocardiographic LVET measurements showed significant correlation (r = 0.53 with P = 0.0084 before bed rest and r = 0.73 with P 0.05 on the last day of bed rest). The shortening of LVET during HDT bed rest measured with both approaches was highly concordant in their effect direction, with a concordance rate of 0.96. Our results also demonstrated a significant decrease of LVETI (P 0.0001) and QS2I (P = 0.0992) and a prolongation of PEPI (P = 0.0049) and PEP/LVET (P = 0.0003) during HDT bed rest over 60 days. Four days after bed rest, LVETI recovered completely to its baseline value. Owing to the relationship between shortening of LVETI and heart failure progression, the easy-to-use oscillometric method might not only be a useful way to evaluate the cardiovascular system during space flights, but could also be of high value in a clinical setting.

Transcranial Direct Current Stimulation (tDCS) has shown that stimulation of Dorsolateral Prefrontal Cortex (DLPFC) facilitates task performance in working-memory tasks. However, little is known about its potential effects on effort. This study examined whether tDCS affects effort during a working-memory task. Participants received anodal, cathodal and sham stimulation over DLPFC across three sessions before carrying out a 2-back task. During the task, effort-related cardiovascular measures were recorded—especially the Initial Systolic Time Interval (ISTI). Results showed that anodal stimulation produced a shorter ISTI, indicating a greater effort compared to cathodal and sham conditions, where effort was lower. These findings demonstrate that anodal stimulation helps participants to maintain engagement in a highly demanding task (by increasing task mastery), without which they would otherwise disengage. This study is the first to show that tDCS impacts the extent of effort engaged by individuals during a difficult task.

Worsening heart failure (HF) is associated with shorter left ventricular systolic ejection time (SET), but there are limited data describing the relationship between SET and clinical outcomes. Thus, the objective was to describe the association between SET and clinical outcomes in an ambulatory HF population irrespective of ejection fraction (EF).We identified ambulatory patients with HF with reduced EF (HFrEF) and HF with preserved EF (HFpEF) who had an outpatient transthoracic echocardiogram performed between August 2008 and July 2010 at a tertiary referral centre. Multivariable logistic regression was used to evaluate the association between SET and 1-year outcomes. A total of 545 HF patients (171 HFrEF, 374 HFpEF) met eligibility criteria. Compared with HFpEF, HFrEF patients were younger [median age 60 years (25th-75th percentiles 50-69) vs. 64 years (25th-75th percentiles 53-74], with fewer females (30% vs. 56%) and a similar percentage of African Americans (36% vs. 35%). Median (25th-75th percentiles) EF with HFrEF was 30% (25-35%) and with HFpEF was 54% (48-58%). Median SET was shorter (280 ms vs. 315 ms, P 0.001), median pre-ejection period was longer (114 ms vs. 89 ms, P 0.001), and median relaxation time was shorter (78.7 ms vs. 93.3 ms, P 0.001) among patients with HFrEF vs. HFpEF. Death or HF hospitalization occurred in 26.9% (n = 46) HFrEF and 11.8% (n = 44) HFpEF patients. After adjustment, longer SET was associated with lower odds of the composite of death or HF hospitalization at 1 year among HFrEF but not HFpEF patients.Longer SET is independently associated with improved outcomes among HFrEF patients but not HFpEF patients, supporting a potential role for normalizing SET as a therapeutic strategy with systolic dysfunction.

This study determined the beverage hydration index (BHI) and postprandial cardiac autonomic activity after consuming an isotonic beverage (IB) compared to distilled water (DW). Twenty-two participants (50% female; mean ± SD; age, 27 ± 3 year; height, 169.1 ± 12.6 cm; weight, 73.3 ± 13.8 kg; BF%, 23 ± 10%) completed two experimental trials where they consumed 1 L DW or an IB; after which urine volume and cardiac autonomic activity was measured through 240 min. Cardiac autonomic activity was quantified using heart rate (HR), log transformed heart rate variability measures (root mean square of successive R–R intervals; RMSSD; low frequency, LF; and high frequency, HF) and systolic time intervals (pre-ejection period, PEP). BHI was significantly greater after IB consumption at min 0 (MD [95% CI]; 1.31 [0.35, 2.27]), 180 min (0.09 [0.022, 0.16]), and 240 min (0.1 [0.03, 0.17]) compared to DW (p = 0.031). Net fluid balance was significantly greater in IB than DW at 180 min (90 [−16.80, 196.81]) and 240 min (106 [−13.88, 225.88]) (p = 0.037). HR decreased over time in both beverage trials but was higher following IB ingestion at 0 min (3.9 [−2.42, 10.22]), 30 min (5.3 [−0.94, 11.54]), and 60 min (2.7 [−3.42, 8.82]) (p = 0.0002). lnHF was greater 30 min post DW ingestion compared to IB (0.45 [−0.23, 1.13]) (p = 0.039). IB promotes greater fluid retention capacity compared to DW within 4 hours of consumption. The variations in cardiac autonomic measures may warrant further investigation in clinical populations (i.e., patients with autonomic failure).

Hamdi Boubaker,1,2 Mohamed Habib Grissa,1,2 Kaouther Beltaief,1,2 Zohra Dridi,3 Mohamed Fadhel Najjar,4 Wahid Bouida,1,2 Riadh Boukef,5 Soudani Marghli,6 Semir Nouira1,2 1Department of Emergency, Fattouma Bourguiba University Hospital, 2Research Laboratory (LR12SP18), University of Monastir, 3Department of Cardiology, 4Department of Biochemistry, Fattouma Bourguiba University Hospital, Monastir, 5Department of Emergency, Sahloul University Hospital, Sousse, 6Department of Emergency, Tahar Sfar University Hospital, Mahdia, Tunisia Background: The goal of this study was to determine the value of systolic time intervals and their change during Valsalva maneuver (VM) in the diagnosis of left ventricular dysfunction (LVD) in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD).Methods: We included 166 patients admitted to the emergency department for AECOPD. Measurement of systolic time intervals included electromechanical activation time (EMAT), left ventricular ejection time (LVET), and EMAT/LVET ratio. These were performed at baseline and during the first strain phase of the VM using a computerized phonoelectrocardiographic method. The diagnosis of LVD was determined on the basis of clinical examination, echocardiography, and brain natriuretic peptide. The values of systolic time intervals were compared between patients with and without LVD; their diagnostic performance was assessed using the area under receiver operating characteristic (ROC) curve.Results: Patients with LVD (n=95) had a significantly higher EMAT and lower LVET and EMAT/LVET ratio compared to patients without LVD (n=71); the area under ROC curve was 0.79, 0.88, and 0.90, respectively, for EMAT, LVET, and EMAT/LVET ratio. All baseline systolic time intervals changed significantly during VM in patients without LVD but they did not change in patients with LVD. The area under ROC curve increased to 0.84 and 0.93,­respectively, for EMAT and EMAT/LVET ratio but did not change for LVET.Conclusion: Simple and noninvasive measurements of systolic time intervals combined with VM could be helpful to detect or rule out LVD in patients admitted to the emergency room for COPD excacerbation. The EMAT/LVET ratio seems to have the best diagnostic value. Keywords: chronic obstructive pulmonary disease, exacerbation, systolic time intervals, Valsalva maneuver&nbsp

Objective: We investigated the repeatability of systolic time intervals (STIs) in healthy subjects using a combination of seismocardiogram (SCG) and electrocardiogram (ECG). STIs have been extensively used in the past to quantify heart performance, particularly the left ventricle. In this study, STIs included pre-ejection period (PEP), left ventricular ejection time (LVET), and their ratio. Approach: We conducted the repeatability test of STI estimation through two experiments. The first involved three consecutive one-minute recordings separated by one-minute intervals, and the second involved two one-minute recordings separated by 24 hours. Twenty healthy subjects participated in our study. We considered the coefficient of variation (CV) to quantify the repeatability. As there was no agreed upon values for optimal CV values, we compared our results with an alternative method using a combination of impedance cardiography (ICG) and ECG. Similar to our method, the alternative method was noninvasive and could be employed for personal heart monitoring. We also studied the repeatability after STIs were corrected for heart rate using two approaches. The first approach used a multiplicative factor per subject based on the heart rates in each recordings of that subject. The second approach employed sex-specific regression models for all subjects (Weissler's equations). Main results: We found that the repeatability of our method (SCG and ECG) was in agreement with the alternative method (ICG and ECG) in both experiments. Moreover, the Weissler's equations approach for heart rate increased the repeatability. Significance: It can be concluded that estimation of PEP, LVET and their ratio through SCG and ECG signals was repeatable in healthy subjects.

Aims: The renal systolic time intervals (STIs), including renal pre-ejection period (PEP), renal ejection time (ET), and renal PEP/renal ET measured by renal Doppler ultrasound, were associated with poor cardiac function and adverse cardiac outcomes. However, the relationship between renal hemodynamic parameters and arterial stiffness in terms of brachial-ankle pulse wave velocity (baPWV) has never been evaluated. The aim of this study was to assess the relationship between renal STIs and baPWV. Methods: This cross-sectional study enrolled 230 patients. The renal hemodynamics was measured from Doppler ultrasonography and baPWV was measured from ABI-form device by an oscillometric method. Results: Patients with baPWV ≧ 1672 cm/s had a higher value of renal resistive index (RI) and lower values of renal PEP and renal PEP/ET (all P< 0.001). In univariable analysis, baPWV was significantly associated with renal RI, renal PEP, and renal PEP/renal ET (all P< 0.001). In multivariable analysis, renal PEP (unstandardized coefficient β = -3.185; 95% confidence interval = -5.169 to -1.201; P = 0.002) and renal PEP/renal ET (unstandardized coefficient β = -5.605; 95% CI = -10.217 to -0.992; P = 0.018), but not renal RI, were still the independent determinants of baPWV. Conclusion: Our results found that renal PEP and renal PEP/renal ET were independently associated with baPWV. Hence, renal STIs measured from renal echo may have a significant correlation with arterial stiffness.

Systolic time intervals (STIs) provide noninvasive insights into cardiac sympathetic neural activity (cSNA). As the effect of exercise intensity on postexercise STI recovery is unclear, this study investigated the STI recovery profile after different exercise intensities. Eleven healthy males cycled for 8 min at 3 separate intensities: LOW (40%–45%), MOD (75%–80%), and HIGH (90%–95%) of heart-rate (HR) reserve. Bio-impedance cardiography was used to assess STIs – primarily pre-ejection period (PEP; inversely correlated with cSNA), as well as left ventricular ejection time (LVET) and PEP:LVET – during 10 min seated recovery immediately postexercise. Heart-rate variability (HRV), i.e., natural-logarithm of root mean square of successive differences (Ln-RMSSD), was calculated as an index of cardiac parasympathetic neural activity (cPNA). Higher preceding exercise intensity elicited a slower recovery of HR and Ln-RMSSD (p < 0.001), and these measures did not return to baseline by 10 min following any intensity (p ≤ 0.009). Recovery of STIs was also slower following higher intensity exercise (p ≤ 0.002). By 30 s postexercise, higher preceding intensity resulted in a lower PEP (98 ± 14 ms, 75 ± 6 ms, 66 ± 5 ms for LOW, MOD, and HIGH, respectively, p < 0.001). PEP recovered to baseline (143 ± 11 ms) by 5 min following LOW (139 ± 13 ms, p = 0.590) and by 10 min following MOD (145 ± 17 ms, p = 0.602), but was still suppressed at 10 min following HIGH (123 ± 21 ms, p = 0.012). Higher preceding exercise intensity attenuated the recovery of indices for cSNA (from STIs) and cPNA (from HRV) in a graded dose–response fashion. While exercise intensity must be considered, acute recovery may be a valuable period during which to concurrently monitor these noninvasive indices, to identify potentially abnormal cardiac autonomic responses.

The aim of this study was to evaluate the use of renal systolic time intervals measured by electrocardiographic gated Doppler ultrasonography for predicting adverse cardiac events. This longitudinal observation study enrolled 205 patients. Renal systolic time intervals, including pre-ejection period (PEP) and ejection time (ET), and ratio of renal PEP to ET, were measured by electrocardiographic gated Doppler ultrasound. The 14 adverse cardiac events identified in this population included 9 cardiac deaths and 5 hospitalizations for heart failure during an average follow up of 30.9 months (25th–75th percentile: 30–33 months). Renal PEP (hazard ratio = 1.023, P = 0.001), renal ET (hazard ratio = 0.975, P = 0.001) and renal PEP/ET (per 0.01 unit increase, hazard ratio = 1.060, P

This study investigated non-invasive indices of post-exercise parasympathetic reactivation (using heart rate variability, HRV) and sympathetic withdrawal (using systolic time intervals, STI) following different exercise durations. 13 healthy males (age 26.4 ± 4.7 years) cycled at 70% heart rate (HR) reserve for two durations—8 min (SHORT) and 32 min (LONG)—on separate occasions: HRV (including natural logarithm of root mean square of successive differences, Ln-RMSSD) and STI (including pre-ejection period, PEP) were assessed throughout 10 min seated recovery. Exercise HR was similar between SHORT and LONG (146 ± 7 and 147 ± 6 b min−1, respectively; p = 0.173), as was HR deceleration during 10 min recovery (p = 0.199). HR remained elevated above baseline (p

The aims of this study were to investigate the correlation between renal and cardiac STIs, including pre-ejection period (PEP), ejection time (ET), and PEP/ET, and to assess the diagnostic values of renal STIs in predicting left ventricular ejection fraction (LVEF) 0.46 in prediction of LVEF

Siemocardiography is a non-invasive technique for cardiomechanical assessment by analyzing the local vibrations on chest surface which can be readily acquired from cost-effective accelerometers. The peaks in siesmocardiogram (SCG) signal correspond to underlying mechanical events in heart cycle and have numerious potential clinical and health-awareness applications. However, utilization of SCG signal requires annotation of these peaks that is challenging due to variations in inter-subject morphology and noise prone characteristics of SCG signal. In this paper, we propose an approach to automatically annotate the desired peaks in SCG signal that are required for systolic time intervals (STI). The approach is based on formulating sliding template for the oncoming beat which is less noisier and hence desired peak detection is easier. The information of peak detected in the sliding template is then used to narrow-down the search of desired peak in actual signal.

Systolic time intervals (STI) and echocardiography were recorded in 133 (70 men, 63 women) newly diagnosed non-insulin-dependent diabetics aged 45–64 years and in 144 (62 men, 82 women) non-diabetic control subjects of the same age. Both male and female diabetics had significantly increased pre-ejection period/left ventricular ejection time ratio (PEP/LVET) in STI as compared with the respective non-diabetic control subjects. Male diabetics showed a reduced ejection fraction (EF) in echocardiography, but no significant difference was found in this respect between female diabetics and controls. A significant negative correlation was found between 2-hour postglucose serum insulin level and EF in male and female diabetics. After adjusting for the effect of age, coronary heart disease, hypertension, obesity and haemoglobin concentration, male diabetics still had a higher PEP/LVET ratio and a lower EF than male controls. In women, no significant differences were found between diabetics and controls in the PEP/LVET ratio or EF adjusted for the above factors. The results of this study are compatible with the view that impaired left ventricular function may be an early phenomenon in the clinical course of non-insulin-dependent diabetes.

Systolic time intervals (STI) were recorded in 33 newly diagnosed non-insulin-dependent diabetics (19 men, 14 women, aged 44-64 years) before and after 3-8 months' dietary therapy. The mean (+/- SD) fasting blood glucose was 11.1 +/- 2.6 mmol/l before treatment and 7.8 +/- 1.8 at the second examination (p less than 0.001). Concomitantly with the decline in blood glucose concentration, the heart rate corrected pre-ejection period (PEP) decreased from 139 +/- 11.9 to 135 +/- 14.4 msec (mean +/- SD) (p less than 0.05), the heart rate corrected left ventricular ejection time (LVET) increased from 400 +/- 15.1 to 410 +/- 20.7 msec (p less than 0.0025) and the PEP/LVET ratio decreased from 0.39 +/- 0.06 to 0.36 +/- 0.06 (p less than 0.005). When the diabetics were divided into two groups according to the degree of the decline in blood glucose concentration, only those whose fasting blood glucose decreased by greater than or equal to 3 mmol/l showed significant changes in STI. No significant changes were observed in the mean heart rate or systolic blood pressure during the treatment. Cardiac dysfunction occurring in untreated non-insulin-dependent diabetics may be caused by metabolic factors and it may be reversed at least partially by correction of hyperglycemia.

Cardiac effects of ethanol ingestion (1.75 g/kg within 3 hours) were examined in 8 healthy males by echocardiography and systolic time intervals in a controlled study. Heart rate (HR) was increased by 15% (p less than 0.05) during intoxication when blood ethanol (mean +/- SD) was 33.7 +/- 4.1 mmol/l. Left ventricular (LV) end-diastolic dimension was simultaneously shortened by 4% (p less than 0.01) and LV end-systolic dimension by 3% (p less than 0.05). Stroke volume was reduced by 12% (p less than 0.05). Most subjects experienced hangover symptoms 12 hours after the beginning of ethanol intake; blood ethanol was 8.8 +/- 4.0 mmol/l. At this time, HR was raised by 17% (p less than 0.05), ejection fraction by 7% (p less than 0.05), and circumferential fiber shortening velocity by 19% (p less than 0.01); total peripheral resistance was decreased by 17% (p less than 0.001). The resultant increase in cardiac output amounted to 22% (p less than 0.01). In short, the main effect of ethanol at modest blood concentrations was to reduce LV preload without detectably impairing myocardial performance. Hangover was characterized by vasodilation as well as intensified LV myocardial and pump performances.

Systolic time intervals, the pre-ejection period (PEP), left ventricular ejection time (LVET) and PEP/LVET ratio were studied in ten thyrotoxic and ten hypothyroid patients. LVET and PEP intervals were corrected for heart rate (LVETc and PEPc). The measurements were repeated after 1-28 months when the patients were euthyroid following appropriate therapy. Compared with the euthyroid values, the PEPc intervals and PEP/LVET ratios were significantly decreased (p less than 0.01) in the thyrotoxic and increased (p less than 0.001) in the hypothyroid patients. In both groups the LVETc intervals were significantly prolonged (p less than 0.001). In four of the hypothyroid patients the PEP/LVET ratios were markedly increased (above 0.60, mean 0.66), and above 0.41 in the euthyroid state (reference value 0.35 +/- 0.05). In the other hypothyroid patients and in thyrotoxic patients the euthyroid PEP/LVET ratios were within the reference values. The systolic time intervals were not influenced by propranolol therapy in the thyrotoxic patients. Our results suggest increased myocardial contractility unaffected by adrenergic blockade in thyrotoxicosis, and reduced contractility in hypothyroidism.

Left ventricular performance in 54 patients with acute myocardial infarction was studied by means of systolic time intervals (STI) and ejection fraction (EF) determined using radionuclide technique. The data were correlated to clinical parameters of left ventricular heart failure and size of infarction. Thirty-seven patients were studied in the convalescent period with repeated registrations at 6, 10 and 24 weeks. Patients with left ventricular heart failure had markedly depressed EF, significantly different from EF in the non-heart failure group. STI did not show any difference. A strong correlation between infarct size and EF could be demonstrated. STI discriminated significantly transmural from non-transmural infarctions, and presented significant differences between those with normal EF (greater than 50%) and patients with EF below 35%. No significant changes could be found in left ventricular performance during the convalescent period, except for an increase in corrected preejection period (PEPc) probably due to drugs. The correlation between EF and STI was poor, the highest correlation coefficient being 0.55 between EF and the ratio PEP/LVET.

Systolic time intervals have been used to detect and quantify the directional changes of left ventricular function. New methods of recording these cardiac timings, which are less cumbersome, have been recently developed and this has created a renewed interest and novel applications for these cardiac timings. This manuscript reviews these new methods and addresses the potential for the application of these cardiac timings for the diagnosis and prognosis of different cardiac diseases.

In the past decade, there has been a resurgence in the field of unobtrusive cardiomechanical assessment, through advancing methods for measuring and interpreting ballistocardiogram (BCG) and seismocardiogram (SCG) signals. Novel instrumentation solutions have enabled BCG and SCG measurement outside of clinical settings, in the home, in the field, and even in microgravity. Customized signal processing algorithms have led to reduced measurement noise, clinically relevant feature extraction, and signal modeling. Finally, human subjects physiology studies have been conducted using these novel instruments and signal processing tools with promising results. This paper reviews the recent advances in these areas of modern BCG and SCG research.

The usefulness of automated measurements of the systolic time intervals in community screening deserves investigation. The systolic time intervals, including pre-ejection period (PEP), the left ventricular ejection time (LVET), and PEP/LVET were automatically and rapidly determined from signals of electrocardiography, phonocardiography, and pulse volume recording in 1087 residents agedor = 40 years in a community of homogeneous Chinese. Receiver operating characteristics analysis was performed to determine the cutoff values for PEP, ET, and PEP/LVET in predicting high N-terminal pro-brain natriuretic peptide (NT-proBNP). The prevalence of high NT-proBNP was 12.3% in men and 8.3% in women. NT-proBNP was linearly related to both PEP and PEP/LVET, while there was a U-shaped relationship between NT-proBNP and LVET. In men, the sensitivity and specificity in predicting high NT-proBNP levels were 60% and 60%, respectively, for PEPor = 89 ms; 60% and 62% for PEP/LVETor = 0.31; and 63% and 60% for LVET272 ms or LVETor = 310 ms. Various combinations of the criteria further improved either sensitivity or specificity. Women had slightly different cutoff values and performance for the various criteria of abnormal systolic time intervals and their combinations. Automated systolic time intervals appear to be useful in the screening of subjects with high NT-proBNP in a community.

In order to elucidate the beat-to-beat changes of the systolic time intervals (STI) during exercise, we proposed new techniques relating to an adaptive filter and detection algorithms for B- and X-points in the impedance cardiograph (ICG). Six male subjects underwent a ramp bicycle exercise up to maximum intensity during which an ECG, ICG and phonocardiogram (PCG) were continuously measured. Following the application of an adaptive filter, the scaled Fourier linear combiner (SFLC), to the first derivative (dZ/dt) of the base impedance (deltaZ) and PCG waveforms, the B- and X-points were automatically determined. For the B-point detection we used three criteria: the zero-crossing point (B(zero)), the 15% response point (B15%) of the negative peak of the dZ/dt (dZ/dt(min)) and a new algorithm (B(new)). The X-point was separately determined by using the ICG and PCG waveforms. It was found that the shape of the dZ/dt waveform directly affected the determination of the B- and X-points. The B-points determined using B(zero) and B15%, criteria were sometimes unstable caused by the location of a notch preceding the dZ/dt(min) compared to the B(new). The time difference between the X-points measured by the ICG and PCG was mostly within +/- 20 milliseconds but statistically significant. Although a wide variation was seen in R-R intervals, the STI were more stable. The relationships between HR and STI from rest to maximal exercise showed a gentle curvilinear relationship. It is suggested that the STI can be obtained precisely on a beat-to-beat basis by using the adaptive filter and detection algorithms for the inflection points of the ICG even during maximum exercise.

We speculated that stroke volume would be higher and heart rate would be lower when the head and upper trunk were mainly upright in the Fowler's position. We therefore analyzed the effects of three trunk postures in Fowler's position on heart rate, blood pressure and circulatory volume.Heart rate (HR), blood pressure (BP), stroke volume (SV), cardiac output (Q), systemic vascular resistance (SVR), ejection time (ET) and pre-ejection period (PEP) were measured in 10 healthy male volunteers (mean age±SEM, 20.7±0.5y; range, 19–23y) while in three trunk postures in Fowler's position. Stroke volume and Q were measured using impedance cardiography. The three trunk postures were 30° of lower and upper trunk inclination (WT30°), 30° and 60° of lower and upper trunk inclination (UT 60°), respectively and 60° of upper and lower trunk inclination (WT60°).Both SV and ET were significantly higher and HR and PEP were lower at UT60° than at WT60° (p0.05). None of Q, SVR and BP significantly differed among the three conditions (p>0.05).These findings suggested that SV and preload are higher when the upper trunk is upright (UT60°) than when the entire trunk is upright (WT60°) while in Fowler's position. In addition, Q might be maintained without increasing HR through vagal withdrawal when only the upper trunk is upright in healthy young males in Fowler's position.

In patients with a load-induced cardiac dysfunction (LCD), the left ventricular (LV) stroke work is supernormal at rest, but then becomes subnormal during handgrip (HG). The LCD usually occurs in children with the mitral valve prolapse (MVP). Our catheterization study revealed that the end-diastolic pressure (EDP) of both ventricles was elevated in LCD patients. In this study, the LV and right ventricular (RV) systolic time (ET) were measured by echocardiograms. The mitral inflow peak velocities, E and A, were also measured by the pulsed Doppler method. Subjects were divided into four groups, each consisting of 16 individuals: group 1, normal children; group 2, LCD patients; group 3, recovered children from LCD, the same individuals as group 2, but after coenzyme Q10 (CoQ) therapy; and group 4, asymptomatic children with MVP. In group 2, the mean PEP and PEP ET were significantly smaller and the peak A velocity was significantly larger than in groups 1, 3 and 4. Among groups 1, 3 and 4, no intergroup differences were found regarding the PEP ET and A. In LCD patients, a depressed inotropic state of the myocardium may result in a high EDP due to the Frank-Starling mechanism, and such a high EDP may then cause STI changes and a large A velocity. CoQ may also return abnormal STIs in LCD patients to normal, probably by improving the inotropic state and, as a consequence, reducing the high EDP of the LV and RV to a normal level.

To complete the existing treatment guidelines for all tumor types, ESMO organizes consensus conferences to better clarify open issues in each disease. In this setting, a consensus conference on the management of lymphoma was held on 18 June 2011 in Lugano, immediately after the end of the 11th International Conference on Malignant Lymphoma. The consensus conference convened ∼45 experts from all around Europe and selected six lymphoma entities to be addressed; for each of them three to five open questions were to be discussed by the experts. For each question, a recommendation should be given by the panel, supported by the strength of the recommendation based on the level of evidence. This consensus report focuses on the three most common lymphoproliferative malignancies: diffuse large B-cell lymphoma, follicular lymphoma and chronic lymphocytic leukemia. A second report will concentrate on mantle cell lymphoma, marginal zone lymphoma and T-cell lymphomas.

Either decreased renal function or increased systolic time interval is associated with cardiac hypertrophy and poor cardiac outcome. The aim of this study was to evaluate combination of renal function and brachial systolic time intervals were associated with increased left ventricular mass index (LVMI) and left ventricular hypertrophy (LVH). In total of 990 patients were consecutively included in this study from January 2011 to December 2012. All study participants were further classified into 4 groups by the values of estimated glomerular filtration rate (eGFR) and ratio of brachial preejection period (bPEP) to brachial ejection time (bET). The classification of 4 groups were eGFR ≥ 45 mL/min/1.73 m2 and bPEP/bET

The aim of this paper is the presentation of recent advancements in impedance cardiography regarding methodical approach, applied equipment and clinical or research implementations. The review is limited to the papers which were published over last 17 months (dated 2011 and 2012) in well recognised scientific journals.

Arterial stiffness is correlated with left ventricular hypertrophy (LVH) and is susceptible to left ventricular performance. Therefore, if left ventricular systolic function is unknown, the relationship between arterial stiffness and LVH is controversial. This study was to assess the impact of the ratio of brachial pre-ejection period (bPEP) to brachial ejection time (bET), a marker of left ventricular systolic function, on the relationship between brachial-ankle pulse wave velocity (baPWV) and LVH.A total of 1146 patients were included in the study. The baPWV and bPEP/bET were measured using an ABI-form device. Patients were classified into four groups. Groups 1, 2, 3, and 4 were patients with bPEP/bET ≤ 0.38 and baPWV below the median, bPEP/bET0.38 but baPWV below the median, bPET/bET ≤ 0.38 but baPWV above the median, and bPET/bET0.38 and baPWV above the median, respectively.Patients in groups 3 and 4 (high baPWV) and patients in group 2 (low baPWV but high bPEP/bET) were associated with increased left ventricular mass index (LVMI) and LVH (all P0.001). In a multivariate model, baPWV was significantly associated with LVMI (P = 0.007) and LVH (P = 0.025). Further adjustment for bPEP/bET made the association between baPWV and LVMI (P = 0.150) and LVH (P = 0.173) disappear.The bPEP/bET has an important impact on the relationship between baPWV and LVH. Therefore, the value of bPEP/bET obtained from the same examination should be considered while interpreting the relationship between baPWV and LVH.

Thoracocardiography noninvasively estimates left ventricular performance by recording ventricular volume curves with inductive plethysmography. We studied timing of these curves to evaluate their potential to accurately track systolic time intervals in comparison with standard methods. Thoracocardiographic left ventricular volume curves, carotid pressure pulses determined by applanation tonometry, the phonocardiogram and ECG were recorded simultaneously in ten normal subjects at various body positions achieved with a tilt table. An equation was derived to predict preejection period from onset of ejection in thoracocardiographic curves. Ventricular ejection time was calculated as total electromechanical systole obtained by phonocardiography minus preejection period. The equation was validated prospectively in 31 measurements in critically ill patients. In normal subjects, the interval ECG Q wave to ejection onset in thoracocardiographic curves correlated well with preejection period from applanation tonometry and phonocardiography (r = 0.92; standard error of estimate (SEE), 8 ms; p0.001). Thoracocardiographic curves showed a delay that varied with body position according to the regression equation: delay = 40 ms + 10 x sine (tilt angle) (where r = 0.62; SEE, 7 ms; p0.001). Application of this equation in the prospective study in patients revealed close agreement in systolic time intervals from thoracocardiography and simultaneous applanation tonometry plus phonocardiography, respectively. The mean difference +/- SD between methods in preejection periods was 3 +/- 7 ms and in the ratios of preejection period to left ventricular ejection time, 0.02 +/- 0.05. Trends of changes in systolic time intervals were identical for the two methods. We conclude that thoracocardiography combined with phonocardiography provides accurate systolic time intervals when corrected for a position-dependent delay of its waveforms.

This study was designed to assess the usefulness of the changes in left ventricular (LV) systolic time intervals after phenylephrine administration for detecting hightisk patients soon after acute myocardial infarction by correlation with the angiographic and ventriculogmphic findings. The procedure was performed in 76 consecutive patients (group I) on the fourth postinfarction day and in 12 normal subjects (group II) free of coronary artery disease. In 20 patients with LV ejection fraction ≤ 40% (subgroup IA) the preejection period (PEP)/LV ejection time (ET) ratio increased from 0.410 ± 0.107 to 0.535 ± 0.102 (p = 0.01) after phenylephrine, whereas in the remaining 56 patients (subgroup IB) with LV ejection fraction >40% and in the 12 normal subjects the PEP/LVET increased nonsignificantly. Of patients with LV ejection fraction >40% a subset of 20 patients was distinguished with proximal stenosis in both left anterior descending and either a dominant right or left circumflex coronary artery (subset IB-a). In these the PEP/LVET increased from 0.347 ± 0.056 to 0.445 ± 0.019 (p = 0.0001) after phenylephrine, whereas in the remaining 36 patients (subset IB-b) without proximal lesions in 2 main arteries the PEP/LVET increased nonsignificantly. In conclusion, the PEP/LVET response to phenylephrine administration early after acute myocardial infarction is a precise, safe, noninvasive bedside method for early stratification of these patients.

Right ventricular systolic time intervals (RVSTI) and noninvasive Doppler-derived pulmonary blood flow were measured before and after surgical ductus ligation in 18 otherwise healthy infants and children who were older than 3 months of age. Right ventricular preejection period (PEP) and the ratio of preejection period and right ventricular ejection time (PEP/RVET), both corrected or uncorrected for heart rate, decreased significantly following surgery (PEP 71 +/- 14 vs. 50 +/- 13, p0.001 and PEP/RVET 0.29 +/- 0.06 vs. 0.21 +/- 0.05, p0.001). The volume of pulmonary blood flow correlated with PEP/RVET (r = 0.48, p = 0.003). The magnitude of the change in pulmonary blood flow correlated with the change in PEP/RVET (r divided by 0.56, p = 0.016). The velocity of circumferential fiber shortening (VCFc) increased after surgery, but not significantly. We speculate that patent ductus arteriosus has a similar effect on right ventricular performance when other congenital heart defects are present.

Heart rate-corrected STI integrate and reflect changes in ventricular inotropy, preload and afterload. STI represent a global method for the evaluation of cardiovascular performance, provided very well controlled study designs, including positive and negative controls and strictly standardised conditions are followed. STI are accurate, economic, reproducable and are very sensitive. They represent a useful non-invasive tool in clinical pharmacology for assessing the influence of drugs, their dose-effect relationships, and the time course of their effects on the cardiovascular system.

Autonomic nervous system (ANS) specificity of emotion remains controversial in contemporary emotion research, and has received mixed support over decades of investigation. This study was designed to replicate and extend psychophysiological research, which has used multivariate pattern classification analysis (PCA) in support of ANS specificity. Forty-nine undergraduates (27 women) listened to emotion-inducing music and viewed affective films while a montage of ANS variables, including heart rate variability indices, peripheral vascular activity, systolic time intervals, and electrodermal activity, were recorded. Evidence for ANS discrimination of emotion was found via PCA with 44.6% of overall observations correctly classified into the predicted emotion conditions, using ANS variables (z=16.05, p

To evaluate the responsible factors for left atrial ejection, the left atrial preejection period (LAPEP), i.e., the time interval between atrial pacing pulse and onset of atrial ejection, and left atrial ejection time (LAET), i.e., the duration of atrial ejection, were determined from mitral inflow velocity patterns in 35 patients with various heart diseases using pulsed Doppler echocardiography. LAPEP ranged from 75 to 157 (mean 110 +/- 18) msec and LAET from 80 to 169 (mean 124 +/- 19) msec. The left atrial dimension before atrial contraction showed no significant correlation with LAPEP or LAET. Peak velocity during atrial contraction was negatively correlated with LAPEP (r = -0.42, p less than 0.05) and positively with LAET (r = 0.56, p less than 0.01). Left ventricular end-diastolic pressure (LVEDP) indicated a significant negative linear correlation with LAET (r = -0.44, p less than 0.05). LAPEP showed no significant linear correlation with LVEDP, but a significant curvilinear relationship was observed between them (LAPEP = 169 - 9.LVEDP + 0.28.LVEDP2, r = 0.63, p less than 0.001). Mean pulmonary capillary wedge pressure (mPCWP) was curvilinearly related to LAPEP (LAPEP = 168 - 11.mPCWP + 0.42.mPCWP2, r = 0.72, p less than 0.001) and LAET (111 + 4.1.mPCWP - 0.22.mPCWP2, r = 0.63, p less than 0.001). Although LAPEP decreased and LAET increased with increase in mPCWP up to about 15 mmHg, the reverse situation was noted for greater mPCWP. Thus, the major determinants of left atrial systolic time intervals are left atrial and ventricular pressures, and peak velocity during atrial contraction.

Right ventricular (RV) systolic time intervals (STIs) have been shown to accurately reflect RV function in patients with acute respiratory distress syndrome (ARDS). The measurement of RVSTIs requires phonocardiography to define the time of RV end systole. If RV end-systolic pressure (RVESP) can be derived from peak pulmonary artery (PA) systolic pressure, then the time of RV end systole, and hence, RVSTIs can be deduced without phonocardiography. We tested this possibility. In 34 patients with ARDS, RVESP was determined on the PAP curve at RV end systole, which was defined by phonocardiography. The ratios of RVESP/peak PA systolic pressure were obtained in each patient, the mean of which was 0.90 +/- 0.006. With an application of this value, the estimated RVSTIs were determined in other groups of patients. Right ventricular end-systolic pressure was estimated from the peak PA systolic pressure by multiplying 0.9. Then the point of RV end systole was determined on the electrocardiographic tracing that coincided with the point of RVESP on the PAP curve by simultaneous display of electrocardiograph and PAP curve. Total electromechanical systole was measured from the onset of the QRS complex to the point of RV end systole on the electrocardiograph. The onset of RV ejection was defined by PAP curve. The validity of this estimated RVSTIs was tested by comparing with the measured RVSTIs. By Bland-Altman analysis, the mean difference in RVSTIs between the two methods was 0.007, and bias was 0.0036, suggesting close agreement. The estimated RVSTIs can be used to accurately assess RV function.

In a double-blind clinical study, electrocardiogram, blood pressure and systolic time intervals were measured in 40 depressive patients treated with either paroxetine (30 mg/day) or amitriptyline (150 mg/day) for 6 weeks. While amitriptyline significantly increased the heart rate, the QTc interval and the PEP/LVET ratio, paroxetine did not alter any of the cardiovascular parameters measured.

Measurement of the pre-ejection period (PEP) can give valuable information on myocardial function in rats. Depressed cardiac function is accompanied by prolongation of PEP, which shortens when cardiac function improves. Left ventricular ejection time (LVET) may be shortened with ageing in spontaneously hypertensive rats.

Two experiments were carried out to investigate the cardiovascular responses of vibration-exposed workers to autonomic stimulation. In the first experiment blood pressures, heart rate and systolic time intervals (STI) were measured during a cold test in 63 vibration-exposed foundry workers and 41 controls. STI, such as total electromechanical systole (QS2I) and left ventricular ejection time index (LVETI), were found to be shorter in the vibration-exposed workers with and without vibration white finger (VWF) than in the controls, both at rest and during cold provocation and recovery (p less than 0.001). A significant inverse relationship between urinary excretion of free catecholamines and the duration of STI was observed under resting conditions (0.001 less than p less than 0.03). In the second experiment, the above mentioned cardiovascular parameters were measured in 11 grinding operators with VWF and 11 controls during a hand grip test, an arithmetic test and an orthostatic test. Finger systolic pressures (FSP) during local cooling to 30, 15 and 10 degrees C were also measured. QS2I and LVETI were more abbreviated in the VWF subjects than in the controls at rest and during both the circulatory stress tests and the recovery periods (0.001 less than p less than 0.05). The reduction in FSP by local cooling from 30 degrees C to 15 and 10 degrees C was greater in the VWF workers than in the controls (p less than 0.001). Significant correlations were observed between the reduction in FSP at 15 and 10 degrees C and the duration of STI during circulatory stress activities (p less than 0.01). A multiple regression analysis pointed out that vibration exposure was the major determinant of STI during circulatory stress, while the importance of age and smoking and drinking habits in predicting STI was negligible. The findings of these studies suggest that the level of cardiac sympathetic activity is increased in VWF workers in comparison with controls. These experimental results are consistent with those of other investigators, indicating that excessive sympathetic reflex activity plays an important role in the pathogenesis of VWF.

Impedance cardiography was introduced over 20 years ago as a noninvasive and unobtrusive technique for measuring systolic time intervals and cardiac output. Although our understanding of the physiological events reflected in the impedance cardiogram has become more refined, the technique's theoretical basis remains somewhat controversial and acceptance of its validity has relied heavily upon empirical validation. Largely as a consequence of this status, there have been inadequate grounds on which to develop sound methodological standardization. Currently, the methodological approaches that have been most frequently adopted may be viewed as representing the standard. The various aspects of impedance methodology are discussed, and alternative approaches described, with the objective of providing an informed basis for choosing among these methodological alternatives. It is recommended that studies utilizing impedance cardiography should be reported with clear and detailed methodological description. This should help clarify the extent to which methodological differences may underlie any discrepant research observations, as well as facilitate the emergence of improved methodological standards.

New filtering algorithms; a modified scaled Fourier linear combiner (mSFLC) and a modified ensemble averaging (mEA) are proposed to remove the phase distortion of the impedance waveform caused by SFLC. Performance of the filters is assessed from the shape of the filtered waveform and the estimation of systolic time intervals. It was found that the mSFLC and mEA could compensate for drawbacks of the SFLC and precisely reproduce the impedance waveforms; however, misinterpretation and attenuation in the cardiac variables may be caused when abrupt changes or irregularities occur in the source waveform.

Thoracic electrical bioimpedance (TEB) provides a rapid, accurate, cost-effective method of optimizing the atrioventricular delay in dual-chamber pacemakers. In addition to measurements of cardiac output, TEB provides other hemodynamic indices such as systolic time interval, left cardiac work index, and end diastolic index. The availability of this additional data can assist the clinician in the objective determination of the optimal atrioventricular delay for individual patients. Thoracic electrical bioimpedance is completely noninvasive and takes only minutes to perform.

Left ventricular (LV) performance can be evaluated noninvasively by determination of systolic time intervals including the preejection period (PEP) of the left ventricle and the ratio of the LV preejection period/LV ejection time (PEP/LVET).1–5 To our knowledge, no new systolic time interval with a sufficient potential for predicting LV performance has been widely used clinically since the inception of the PEP and PEP/LVET. In this study we evaluated LV performance using a new systolic time interval obtained by continuous-wave Doppler echocardiography and electrocardiography. In addition, we compared the effectiveness of this new systolic time interval with that of the established time intervals for evaluating left ventricular performance.

FmmEi.CakdathofQRSurbudng~IandaVFin pathtswllhnonndaxls(A),leflaxkdevlatl6n(B)and lightward axh (c) (see text). QRS deflection in aVF is negative. Similarly, in Figure 1 C, the angle of 1 I .2” is added to 90” (lead aVF, largest net QRS defection) since the net QRS deflection in lead I is negative. Rapid calculation of the electrocardiographic frontal axis is desirable. The method described is simple and provides an acceptable approximation of the axis determined using the trigonometric tangent. The calculated angle may underestimate the true angle by less than 4.1 O without overestimation. Alternative methods to determine the axis are reliable but may require the use of tables or reference diagrams.3-6 Thus, advantages of this formula include its simplicity, which allows for rapid calculation of frontal plane axis without use of the more cumbersome hexaxial reference diagram or tables. It may be particularly useful where there is no equiphasic lead, such that Grant’s method’ is not easily applicable. The mean frontal plane axis may vary by 35O in an individual patient when different lead combinations are used.’ When more accurate determination is desired, an average of several lead combinations may be useful.’

We evaluated the value of serum-free thyroid hormone and thyrotropin (TSH) concentrations in the detection of peripheral hyperthyroidism during thyroxine suppression therapy. A total of 57 patients on a stable thyroxine dose and 70 controls participated in the study. Serum-free thyroxine (FT4), free triiodothyronine (FT3) and TSH were measured by immunoassays based on time-resolved fluorescence (Delfia). The assay for TSH was a modification of a third generation Delfia hTSH Ultra method. The patients were classified into euthyroid and hyperthyroid subgroups based on clinical signs and symptoms (Wayne index). Systolic time intervals (STI) were measured. The Wayne indices were higher among patients than controls (p0.0001). The STI results were similar in patients and controls. Only FT4 had the discriminatory power for classifying euthyroid and hyperthyroid patients according to discriminant analyses. The diagnostic value of FT4 was further assessed by calculating the area under the relative operating characteristic (ROC) curve. The area was 0.707 (SE 0.0918), which was significantly different from an area of 0.5, i.e. the area of a test of no value (p = 0.032). In conclusion, a high serum FT4 concentration indicates hyperthyroidism during long-term thyroxine treatment among thyroid carcinoma patients. Although the degree of TSH suppression can now be exactly monitored with new third generation TSH assays, hyperthyroidism cannot be defined using TSH concentration in thyroid carcinoma patients. Therefore, additional serum FT4 concentration assays are needed in the assessment of hyperthyroidism associated with TSH suppression therapy in thyroid carcinoma patients.

Echocardiographic assessments of fetal and neonatal systolic time intervals were made to determine differences in circulatory changes in 40 neonates delivered vaginally and 30 delivered by elective cesarean section. Left preejection period (LPEP), left ventricular ejection time (LVET), LPEP/LVET, right preejection period (RPEP), right ventricular ejection time (RVET), RPEP/RVET, and heart rate were determined at various time points from antenatal to 120 hours after delivery. There were no significant changes in left systolic time intervals between the two groups at any various time points. However, RPEP and RPEP/RVET values were significantly higher in the cesarean section group than in those in normal vaginal delivery group within 12 hours after delivery. These results suggest that the transient pulmonary hypertension after delivery is prolonged in babies delivered by elective cesarean section.

This study was undertaken to compare results of modern serum thyroid hormone assays with cardiac systolic time intervals (STI) during thyroxine treatment in hypothyroid patients. The patients were assessed clinically (Billewicz index) and the STI and serum thyrotropin (TSH), total and free thyroxine (T4) and total and free triiodothyronine (T3) were determined in 16 hypothyroid women (Group I) treated with 50 micrograms increments of thyroxine, and in 13 women who had a history of thyroid carcinoma and high-dose thyroxine replacement therapy and had elevated thyroid hormone concentrations (Group II). The STI of 24 matched healthy female controls were used for reference of STI. The pre-ejection period (PEP) index and the PEP/LVET ratio (left ventricular ejection period) were greater in untreated overtly and mildly hypothyroid patients (p less than 0.05) than in the controls. During stable thyroxine therapy [mean daily dosage for Group I 137.5 (7.3) micrograms and for Group II 220 (61) micrograms] the PEP correlated with serum free T4 (FT4), as measured by a two-step method (SpectriaR) (r = -0.55, p less than 0.01, n = 29) and total T4 (r = -0.51, p less than 0.05, n = 29), but not with TSH, T3, FT3 or FT4 measured by an analogue method Amerlex-M(R). The TRH test was not valuable in follow-up because of the strong correlation between basal TSH and stimulated TSH values (r = 0.95). In conclusion, STI are useful for assessment of the thyroid state in untreated hypothyroid patients. Serum TSH becomes normal in the same time as STI and is the best for follow-up. If serum TSH is low and the patient is on stable thyroxine therapy, we recommend serum FT4 for monitoring thyroxine replacement. Two-step FT4 assays had the best correlation with STI, which has significance in patients with non-thyroidal illness.

The systolic time intervals (STI) offer temporal description of the sequential phases of cardiac cycle which are influenced physiologically by the same variables as affect other measures of left ventricular (LV) performance. The STI hence offer a measure of ventricular function which augments other measures of ventricular performance. Because of the extreme sensitivity of this variable and the ease of its measurement the STI are well suited for studying the effect of pharmacologic agents upon the heart.

We investigated the effects of dobutamine therapy on myocardial function in premature infants. Left ventricular performance was assessed by measuring left ventricular systolic time intervals: rate-corrected pre-ejection period (PEPI), rate-corrected left ventricular ejection time (LVETI), and pre-ejection period to left ventricular ejection time ratio (PEP/LVET) which was obtained by echocardiography. Measurements were performed in 17 hemodynamically unstable premature infants who had an elevated PEP/LVET ratio before and 30 min after starting dobutamine infusion (10 micrograms/kg.min). Dobutamine infusion resulted in a significant decrease in PEPI (from 108 +/- 16 [SEM] to 95 +/- 17 msec; p less than .01) and in PEP/LVET ratio (from 0.55 +/- 0.16 [SEM] to 0.45 +/- 0.17; p less than .01), and in a significant increase in LVETI (from 255 +/- 15.7 [SEM] to 264 +/- 16.2 msec; p less than .01). Heart rate increased significantly from 146 +/- 17 (SEM) to 163 +/- 16 beat/min; p less than .01. Mean arterial pressure increased in 12 of 14 infants. These results show that dobutamine enhances left ventricular performance in premature infants who have depressed left ventricular function.