Search

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetically mediated cardiomyopathy charac-terized by progressive myocardial loss of the right ventricle and its replacement by fibrofatty tissue, causing dyskinesia, aneurysm, and/or arrhythmia. The prevalence of ARVC is estimated to be 1 in 2,000-5,000, with the condition accounting for up to 20% of sudden cardiac deaths in individuals < 35 years old. This report describes the case of 61-year-old Japanese who was diagnosed with ARVC after cardiac arrest (CA) and successful resusci-tation. After the sudden CA, the restoration of spontaneous circulation was achieved with appropriate resusci-tation, followed by the introduction of target temperature management in the intensive care unit. He was diag-nosed with ARVC based on angiography and histology results. An ICD (implantable cardioverter-defibrillator) was implanted, and he was discharged without neurological sequelae 1 month post-CA. ARVC is an important cause of sudden CA, and successfully resuscitated patients with right ventricular dilation should undergo testing to rule out ARVC.

Although optimal prehospital airway management after out-of-hospital cardiac arrest (OHCA) remains undetermined, no studies have compared different advanced airway management (AAM) policies adopted by two hospitals in charge of online medical direction by emergency physicians. We examined the impact of two different AAM policies on OHCA patient survival.This observational cohort study included adult OHCA patients treated in Okayama City from 2013 to 2016. Patients were divided into two groups: the O group - those treated on odd days when a hospital with a policy favoring laryngeal tube ventilation (LT) supervised, and the E group - those treated on even days when the other hospital with a policy favoring endotracheal intubation (ETI) supervised. Multiple logistic regression analysis was performed to assess airway device effects. The primary outcome measure was seven-day survival.Of 2,406 eligible patients, 50.1% were in the O group and 49.9% were in the E group. O group patients received less ETI (1.0% vs. 12.0%) and more LT (53.3% vs. 43.0%) compared with E group patients. In univariate analysis, no differences were observed in seven-day survival (9.4% vs 10.1%). Multiple regression analysis revealed neither LT nor ETI had a significant independent effect on seven-day survival, considering bag-valve mask ventilation as a reference (OR, 0.78; 95% CI, 0.54 to 1.13, OR, 0.79; 95% CI, 0.36 to 1.72, respectively).Despite different advanced airway medical direction policies in a single city, there were no substantial impact on outcomes for OHCA patients.

Trauma is a primary cause of death globally, with non‐compressible torso hemorrhage constituting an important part of “potentially survivable trauma death.” Resuscitative endovascular balloon occlusion of the aorta has become a popular alternative to aortic cross‐clamping under emergent thoracotomy for non‐compressible torso hemorrhage in recent years, however, it alone does not improve the survival rate of patients with severe shock or traumatic cardiac arrest from non‐compressible torso hemorrhage. Development of novel advanced maneuvers is essential to improve these patients’ survival, and research on promising methods such as selective aortic arch perfusion and emergency preservation and resuscitation is ongoing. This review aimed to provide physicians in charge of severe trauma cases with a broad understanding of these novel therapeutic approaches to manage patients with severe hemorrhagic trauma, which may allow them to develop lifesaving strategies for exsanguinating trauma patients. Although there are still hurdles to overcome before their clinical application, promising research on these novel strategies is in progress, and ongoing development of synthetic red blood cells and techniques that reduce ischemia‐reperfusion injury may further maximize their effects. Both continuous proof‐of‐concept studies and translational clinical evaluations are necessary to clinically apply these hemostasis approaches to trauma patients., This review aimed to provide physicians in charge of severe trauma cases with a broad understanding of these novel therapeutic approaches to manage patients with severe hemorrhagic trauma, which may allow them to develop lifesaving strategies for exsanguinating trauma patients. Although there are still hurdles to overcome before their clinical application, promising research on these novel strategies is in progress.

要旨 歯科治療後に皮下気腫や縦隔気腫を発症した報告は多くみられる。しかし，進行する呼吸困難を呈した報告はない。今回，歯科治療を契機に気道狭窄を伴う深頸部・喉頭気腫が生じ，気道確保を要した1例を報告する。症例は30歳男性。歯科で左下顎智歯水平埋伏歯の分割抜歯のためエアタービンを使用した際，皮下気腫と呼吸困難が出現した。処置を中止し，自宅にて経過をみていたが，徐々に呼吸困難が増悪するため，処置から6時間後に当院を受診した。来院時，左下顎から頸部に広がる皮下気腫を認めた。CT検査で左下顎の粘膜下，両側頸部深部組織，左鎖骨上・喉頭蓋谷の粘膜，縦隔まで広がる広範囲の気腫を認めた。気腫による上気道狭窄が疑われ，気道確保目的に気管挿管，人工呼吸管理を行った。皮下気腫と縦隔気腫は翌日には改善傾向となり，リークを確認して抜管した。入院3日目には独歩退院となった。歯科治療後に呼吸困難を呈した患者では気腫の拡大による上気道狭窄が増悪し，本症例のように気管挿管による気道確保を必要とする場合もあるため，CT検査も活用しながら適切な気道管理を行うことが重要である。

Patients with mobile teeth are at an increased risk of tooth injury related to tracheal intu- bation. Although the presence/absence of mobile teeth is confirmed through interviews during preoperative visits, patients are frequently unaware of the presence of such teeth. In our facility, dental consultation is pro- vided for all patients undergoing thoracoscopically- assisted surgery as part of the management of oral hygiene. This study examined the presence/absence of mobile teeth reported by patients during preoperative visits and those identified on dental consultation, focus- ing on the inconsistency between them.Patients who had undergone thoraco- scopically-assisted surgery in our facility between Janu- ary and October 2014 were retrospectively studied. Tooth mobility was evaluated using the Miller index.Among the 76 (46 males and 30 females) patients aged 36 to 88 (mean: 67.8), mobile teeth were identified on dental consultation in 13 and reported during preoperative visits by 8.Based on this findings, it may be nec- essary to pay sufficient attention when inserting tubes even when mobile teeth have not been reported by patients during preoperative visits.

In a 53-year-old female patient total thyroidectomy for a giant goiter under general anesthesia was scheduled. On talking, airway stenosis sounds were heard. Cervical to thoracic CT revealed left and right lobe tumors measuring 5.3 x 5.6 x 10.0 and 9.1 x 8.6 x 10.0 cm, respectively. The trachea showed stenosis at a site 3.8 to 6.5 cm below the glottis, and the narrowest lumen diameter was 3.1 mm. Due to marked tracheal stenosis, awake intubation was not selected. To maintain the airway, tracheotomy was performed under local anesthesia. Considering the risk of difficulty in ventilation during tracheostomy, 4 Fr catheter sheaths were inserted into the right femoral artery and vein for percutaneous cardiopulmonary support (PCPS). Subsequently, tracheotomy was conducted in an area peripheral to the site of stenosis. After tracheotomy, general anesthesia was started. During general anesthesia, there were no problems regarding ventilation. The tracheal cannula was removed 7 days after surgery, and the patient was discharged after 14 days. For general anesthesia in patients with giant goiter, it is important to select an airway management method in consideration of tumor-related compression of the trachea. Airway management by tracheotomy under local anesthesia with standby of PCPS may be a treatment option.

Temperature changes influence cardiac diastolic function. The monoexponential time constant (tauE), which is a conventional lusitropic index of the rate of left ventricular (LV) pressure fall, increases with cooling and decreases with warming. We have proposed that a half-logistic time constant (tauL) is a better lusitropic index than tauE at normothermia. In the present study, we investigated whether tauL can remain a superior measure as temperature varies. The isovolumic relaxation LV pressure curves from the minimum of the first time derivative of LV pressure (dP/dtmin) to the LV end-diastolic pressure were analyzed at 30, 33, 36, 38, and 40 °C in excised, cross-circulated canine hearts. tauL and tauE were evaluated by curve-fitting using the least squares method and applying the half-logistic equation, P(t) = PA/[1 + exp(t/tauL)] + PB, and the monoexponential equation, P(t) = P0exp(–t/tauE) + P∞. Both tauL and tauE increased significantly with decreasing temperature and decreased with increasing temperature. The half-logistic correlation coefficient (r) values were significantly higher than the monoexponential r values at the 5 above-mentioned temperatures. This implies that the superiority of the goodness of the half-logistic fit is not temperature dependent. The half-logistic model characterizes the amplitude and time course of LV pressure fall more reliably than the monoexponential model. Hence, we concluded that tauL is a more useful lusitropic index regardless of temperature.

We investigated perioperative management and clinical outcome of 12 patients who were 85 years old or older and received video-assisted thoracic surgery under general anesthesia. Although all the patients had preoperative respiratory complications or cardiovascular complications, they were discharged without any additional respiratory assistance such as home oxygen therapy. Our observation suggests that it is important to evaluate the indication of anesthesia from their daily activities and pulmonary function test even if they are oldest-old. If the patient demonstrates good physical function, he or she should not be excluded from anesthesia.

The logistic time constant (tau(L)) has been proposed as a better index of the rate of left ventricular (LV) relaxation or lusitropism than the conventional monoexponential time constant (tau(E)). However, whether and how the Frank-Starling effect influences tau(L) remains to be elucidated. We compared the effect of LV volume (LVV) loading on both logistic and monoexponential fittings. The isovolumic LV relaxation pressure curves from the maximum negative time derivative of pressure (-dP/dt(max)) were analyzed at 3 different end-points at 4 LVVs of 10, 12, 14, and 16 mL in 8 excised, cross-circulated canine hearts. We found that the logistic fitting was superior to the monoexponential fitting at all LVVs and end-points. LVV loading did not affect tau(L) but affected tau(E) slightly. Although the advancing end-point increased both tau(L) and tau(E), the increases were significantly smaller for tau(L) than for tau(E) at all LVVs. Moreover, the changes in both the amplitude constants and nonzero asymptotes with the advancing end-point were significantly smaller for the logistic fitting than for the monoexponential fitting. We conclude that tau(L) served as a more reliable index of lusitropism that is independent of the change in LVV loading or the Frank-Starling effect.

Background Initial fluid resuscitation is an important hemodynamic therapy in patients with septic shock. The Surviving Sepsis Campaign Guidelines recommend fluid resuscitation with volume loading according to central venous pressure (CVP). However, patients with septic shock often develop a transient decrease in cardiac function; thus, it may be inappropriate to use CVP as a reliable marker for fluid management. Methods We evaluated 40 adult patients with septic shock secondary to intra-abdominal infection who received active treatment and were monitored using transthoracic echocardiography (TTE) and CVP for 2 days after admission to our intensive care unit (ICU). We measured left ventricular end-diastolic diameter (LVEDD), left atrial diameter (LAD), and the pressure gradient of tricuspid regurgitation (TR∆P). The shock status was treated with volume loading and inotrope/vasopressor administration according to the TTE findings. We assessed left ventricular fractional shortening (LVFS) as an index of left ventricular contractility and TR∆P as an index of right ventricular afterload and then examined the correlation between CVP and LVEDD/LAD/TR∆P. Results LVFS decreased to ≤30% in 42.5% and 27.5% of patients with septic shock, and severe left ventricular dysfunction with LVFS ≤20% developed in 12.5% and 15.0% of patients on the first and second ICU days, respectively, despite the use of inotropes/vasopressors. Mild pulmonary hypertension as indicated by TR∆P ≥30 mmHg was present in 27.5% and 30.0% of patients on their first and second ICU days, respectively. There was no significant correlation between CVP and LVEDD/LAD/TR∆P. The hospital mortality rate in this study was 10.0%, although the predicted mortality based on the Acute Physiology and Chronic Health Evaluation II score was 58.7%. Conclusions Our results suggest that CVP is not a reliable marker of left ventricular preload for fluid management during the initial phase of septic shock. Assessment of left ventricular preload, right ventricular overload, and left ventricular contractility using TTE seems to be more informative than the measurement of CVP for fluid resuscitation since some patients developed left ventricular dysfunction and/or right ventricular overload.

We have found that cardiac temperature proportionally changes O2 cost of contractility, defined as O2 consumption for myocardial total Ca2+handling normalized to contractility in terms of the end-systolic pressure-volume ratio (maximal elastance, E max), in the canine left ventricle (temperature sensitivity, Q10 = 2). We have separately found that a decrease in the recirculation fraction (RF) of Ca2+ within myocardial cells underlies an increased O2 cost of E max in stunned hearts. We therefore hypothesized that a similar change in RF would underlie the Q10 of O2 cost of E max. We tested this hypothesis by analyzing RF calculated from an exponential decay component of the transiently alternating postextrasystolic potentiation in the canine left ventricle. RF decreased from 0.7 to 0.5 as cardiac temperature increased from 33 to 38°C with Q10 of 0.5, reciprocal to that of O2 cost of E max. We conclude that Q10 of ATP-consuming reactions involved in Ca2+handling and E max response to it could reasonably account for the reciprocal Q10 of RF and O2 cost of E max.

There are few reports on general anesthesia in survivors of ARDS. Patients after recovery from ARDS are at risk for compromised pulmonary function, neuromuscular weakness and cognitive dysfunction. We report 2 cases of general anesthesia in survivors of ARDS. In Case 1, a 64-year-old man who had recovered from ARDS associated with Legionella pneumonia underwent carotid endarterectomy. In Case 2, a 69-year-old man who had recovered from ARDS associated with pneumococcal pneumonia underwent hepatectomy. Concerning the preoperative assessments, the spirometry data were almost normal but Hugh-Jones classification scale was II in both cases. Diffusion disturbance might be the cause of discrepancies between good respiratory functions and limited daily activities. In both cases, anesthesia was given with propofol, fentanyl remifentanil and sevoflurane. Peak airway pressure was maintained below 15 cmH2O with pressure control ventilation. They were extubated at the end of surgery and there were no serious complications during the perioperative period.

We report a case of a 19-year-old male with rocuronium-induced anaphylactic shock. He was scheduled for endoscopic sinus surgery for chronic sinusitis under general anesthesia. Induction of anesthesia was done with fentanyl, propofol and sevoflurane. Just after administration of rocuronium, he developed tachycardia with extended exanthema on the face, anterior chest wall and abdomen. He was difficult to ventilate manually with mask and then intubated without difficulty. The carotid arterial pulse was not palpable and adrenaline was given intermittently to maintain blood pressure. Although the systolic blood pressure increased to 80 mmHg, hemodynamics was unstable with adrenaline. Sugammadex was then given and the blood pressure became stable without adrenaline. Exanthema also disappeared gradually. He was then transferred to ICU and extubated without any sequela. The plasma beta-tryptase increased to 46 microg x l(-1) during the shock state and returned to 14.1 microg x l(-1) 8 hrs after the event. The blood hemoglobin level also increased to 21.3 g x dl(-1) during the shock state and returned to 17.2 g x dl(-1) during the recovery phase. The laboratory data showed a marked increase in vascular permeability caused by rocuronium-induced anaphylactic shock.

Preoperative forced expiratory volume in 1 second less than 1 l is a risk factor for anesthesia. We report perioperative management and prognosis of 7 patients with restricted lung function who underwent lung resection under general anesthesia. We assessed the patients preoperatively from the point of view of heart-lung functions such as predicted postoperative forced expiratory volume in 1 second greater than 0.8 l, an ability of walking on the level for more than 5 minutes at his own speed without a rest, presence of hypercapnia, and degree of pulmonary hypertension. One patient was extubated on the first postoperative day because of an asthmatic attack, whereas the remaining 6 patients were extubated in the operating room. Although 1 patient developed postoperative complications of lung air leakage and pneumonia, he recovered with conservative therapy. All patients were discharged without any sequela. We were able to manage high-risk patients with limited lung functions successfully during the perioperative period without serious complications.

The Weibull distribution is widely used to analyze the cumulative loss of performance, i.e., breakdown, of a complex system in systems engineering. We found for the first time that the difference curve of two Weibull distribution functions almost identically fitted the isovolumically contracting left ventricular (LV) pressure-time curve [P( t)] in all 345 beats (3 beats at each of 5 volumes in 23 canine hearts; r = 0.999953 ± 0.000027; mean ± SD). The first derivative of the difference curve also closely fitted the first derivative of the P( t) curve. These results suggest the possibility that the LV isovolumic P( t) curve may be characterized by two counteracting cumulative breakdown systems. Of these, the first breakdown system causes a gradual pressure rise and the second breakdown system causes a gradual pressure fall. This Weibull-function model of the heart seems to give a new systems engineering or integrative physiological view of the logic underlying LV isovolumic pressure generation.

We recently found that contractility ( E max) of an individual irregularly arrhythmic beat in electrically induced atrial fibrillation (AF) is reasonably predictable from the ratio of the preceding beat interval (RR1) to the beat interval immediately preceding RR1 (RR2) in the canine left ventricle. Moreover, the monotonically increasing relation between E max and the RR1-to-RR2 ratio (RR1/RR2) passed through or by the mean arrhythmic beat E max as well as the regular beat E max at RR1/RR2 = 1. We hypothesized that this E max-RR1/RR2 relation during irregular arrhythmia could be attributed to the basic characteristics of the mechanical restitution and potentiation. To test this, we adopted a known comprehensive equation describing the force restitution and potentiation as a function of two preceding beat intervals and simulated contractilities of irregular arrhythmic beats with randomized beat intervals on a computer. The simulated E max-RR1/RR2 relation reasonably resembled the one that we recently observed experimentally, supporting our hypothesis. We therefore conclude that the primary mechanism underlying the varying contractilities of irregular beats in AF is mechanical restitution and potentiation.

We have reported that, in canine hearts, cardiac cooling to 29°C enhanced left ventricular contractility but changed neither the contractile efficiency of cross-bridge (CB) cycling nor the excitation-contraction coupling energy. The mechanism of this intriguing energetics remained unknown. To get insights into this mechanism, we simulated myocardial cooling mechanoenergetics using basic Ca2+and CB kinetics. We assumed that both adenosinetriphosphatase (ATPase)-dependent sarcoplasmic reticulum (SR) Ca2+uptake and CB detachment decelerated with cooling. We also assumed that all the ATPase-independent SR Ca2+release, Ca2+binding to and dissociation from troponin, and CB attachment remained unchanged. The simulated cooling shifted the CB force-free Ca2+concentration curve to a lower Ca2+concentration, increasing the Ca2+responsiveness of CB force generation, and increased the maximum Ca2+-activated force. The simulation most importantly showed that these cooling effects combined led to a constant contractile efficiency when Ca2+uptake and CB detachment rate constants changed appropriately. This result seems to account for our experimentally observed constant contractile efficiency under cooling inotropy.

We studied whether intracoronary Ca administration after beta-blockade would increase the internal Ca recirculation fraction (RF) analogously to the Ca administration before beta-blockade. This was performed in excised cross-circulated canine hearts. We analyzed the exponential decay component of the postextrasystolic potentiation (PESP) following a spontaneous extrasystole. All the PESPs decayed in alternans with atrial pacing at a constant rate. We obtained the time constant (tau(e)) of the monoexponential decay component of the alternans PESP. An increment of intracoronary Ca by 1.5 mmol/l enhanced the left ventricular contractility index Emax (end-systolic maximum elastance) by 2.5 times before and after beta-blockade with propranolol. The intracoronary Ca after beta-blockade slightly but significantly increased tau(e), and hence increased RF calculated from tau(e) by RF = exp(-1/tau(e)). This was analogous to the slightly increased tau(e) and RF with Ca before beta-blockade. We speculate that the myocardial cyclic AMP-dependent phosphorylation level would not significantly alter the effect of intracoronarily administered Ca on myocardial Ca handling, in terms of tau(e) and RF.

We report a case of general anesthesia for the removal of pheochromocytoma in a patient complicated with severe hypertrophic obstructive cardiomyopathy. A 65-year-old woman complained of fatigability with hypertension and diabetes mellitus. She was diagnosed as an extra-adrenal peri-aortic pheochromocytoma with severe hypertrophic obstructive cardiomyopathy. The left ventricular outflow gradient (LVOG) was 199 mmHg and the serum noradrenaline level was 13,567 pg x ml(-1) (100-450). As a preoperative management, atenolol, verapamil and disopyramide were given to decrease LVOG. Then doxazosin was given to control hypertension and to increase the circulating blood volume without deteriorating the outflow tract obstruction. LVOG decreased to 50 mmHg preoperatively. Anesthesia was given with propofol, fentanyl, remifentanil and isoflurane with a continuous infusion of diltiazem. The circulating blood volume was maintained with adequate volume loading assessed by the measurement of the left ventricular end-diastolic diameter and LVOG with transesophageal echocardiography. After the removal of the tumor, continuous infusion of noradrenaline was given to maintain the blood pressure. She was extubated in the ICU. LVOG decreased to 20 mmHg with stable hemodynamics on the second postoperative day. She was discharged from the ICU without any adverse cardiac events during the perioperative period.

Acquired hemophilia A (AHA) is an uncommon but potentially life-threatening hemorrhagic disorder caused by the development of an inhibitor against coagulation factor VIII (FVIII). AHA is very rare, affecting approximately 1 in 1 million individuals. However, the incidence may actually be higher, because diagnosis is difficult and the disease can be overlooked. We report a case of an 80-year-old man who presented with sudden onset of severe hemothorax. The patient was diagnosed with presumed AHA based on acute onset of bleeding symptoms and unexplained isolated prolonged activated partial thromboplastin time. Diagnosis was definitely established by demonstrating a decrease in FVIII activity, presence of FVIII inhibitor activity, and normal von Willebrand factor. The patient was successfully treated with recombinant activated coagulation factor VII and transcatheter artery embolization of the intercostal arteries.

We report successful anesthetic management of a 38-year-old man with thyroid storm using an ultra-short acting beta blocker, landiolol. The patient was admitted to the hospital for severe abdominal pain. An emergency laparotomy was scheduled for perforated gastric ulcer under a condition of uncontrolled thyrotoxicosis. On arriving the operating room, he showed tachycardia of 140 beats x min(-1) and blood pressure of 140/75 mmHg and high fever of 39 degrees C with tremor, sweating and diarrhea. He was anesthetized with oxygen, nitrous oxide, sevoflurane and fentanyl. Heart rate was around 130 beats x min(-1), and the landiolol was given continuously at a rate of 0.02-0.04 microg x kg(-1) x min(-1). Heart rate was controlled bellow 120 beats x min(-1) without hypotension during anesthesia. Thiamazole and inorganic iodine were given through an enterostomy tube postoperatively, and heart rate decreased gradually. He was extubated on the third postoperative day without any sequelae.

We report a case of general anesthesia for laparoscopic cholecystectomy at 12 weeks of gestation. A 20-year-old woman weighing 123 kg was admitted with epigastralgia. She was diagnosed as pregnancy of 6 weeks of gestation and acute cholecystitis. Percutaneous trans-gallbladder drainage was performed to delay operation until 12 weeks of gestation. Laparoscopic cholecystectomy was performed uneventfully under general anesthesia combined with epidural anesthesia. There were no clinical signs of fetal distress during the perioperative period.

We have found that a logistic function fits the left ventricular isovolumic relaxation pressure curve in the canine excised, cross-circulated heart more precisely than a monoexponential function. On this basis, we have proposed a logistic time constant (tau(L)) as a better index of ventricular isovolumic lusitropism than the conventional monoexponential time constant (tau(E)). We hypothesize in the present study that this tau(L) would also be a better index of myocardial isometric lusitropism than the conventional tau(E). We tested this hypothesis by analyzing the isometric relaxation force curve of 114 twitches of eight ferret isolated right ventricular papillary muscles. The muscle length was changed between 82 and 100% L(max) and extracellular Ca(2+) concentrations ([Ca(2+)](o)) between 0.2 and 8 mmol/l. We found that the logistic function always fitted the isometric relaxation force curve much more precisely than the monoexponential function at any muscle length and [Ca(2+)](o) level. We also found that tau(L) was independent of the choice of the end of isometric relaxation but tau(E) was considerably dependent on it as in ventricular relaxation. These results validated our present hypothesis. We conclude that tau(L) is a more reliable, though still empirical, index of lusitropism than conventional tau(E) in the myocardium as in the ventricle.

We investigated the effects of myocardial temperature on left ventricular (LV) mechanoenergetics in the excised, cross-circulated canine heart. We used the framework of the LV contractility ( Emax)-pressure-volume area (PVA; a measure of total mechanical energy)-myocardial oxygen consumption (Vo2) relationship. We have shown this framework to be useful to integrative analysis of the mechanoenergetics of a beating heart. In isovolumic contractions at a constant pacing rate, increasing myocardial temperature from 30 to 40°C depressed Emaxand increased the oxygen cost of Emax, which was enhanced by dobutamine, in a linear manner. However, the slope of the Vo2-PVA relation (reciprocal of contractile efficiency) and its Vo2intercept remained constant. Q10values of Emax, the oxygen cost of Emax, and the oxygen cost of PVA were 0.4, 2.1 and 1.0, respectively, around normothermia. We conclude that the temperature-dependent processes of cross-bridge cycling and Ca2+handling integratively depress Emaxand augment its oxygen cost without affecting the oxygen cost of PVA as myocardial temperature increases by 10°C around normothermia.

We previously found that the isovolumic pressure curve of the left ventricle and the isometric twitch force curve of the right ventricular in situ papillary muscle, both of the blood-perfused canine heart, were precisely fitted by our newly proposed hybrid logistic function. This function describes the difference between the two S-shaped logistic functions for the rising and falling components: A/[1+exp{-(4B/A)(t-C)}]-D/[1+exp{-(4E/D)(t-F)}]+G. This function characterizes comprehensively both ventricular and in situ papillary muscle contraction and relaxation. In the present study, we hypothesized that this function could also characterize the force curve of the most popular, standard-type, isolated and Tyrode-superfused papillary muscle preparation. To test this hypothesis, we investigated how precisely the hybrid logistic function could fit 112 isometric twitch force curves observed in eight isolated and Tyrode-superfused ferret right ventricular papillary muscles at different muscle lengths and extracellular Ca2+ concentrations. We always obtained a precise curve fitting with a correlation coefficient above 0.9987. This fitting was much more precise than sinusoidal and polynomial exponential function curve fittings. These results supported the present hypothesis. We conclude that our hybrid logistic function reasonably characterizes the force curve of the isolated myocardial preparation. This result broadens the generality of the hybrid logistic characterization of ventricular isovolumic pressure and myocardial isometric twitch force generation. The hybrid logistic characterization seems to be an integrative expression of contractile processes in myocardial twitch contraction.

We investigated the effects of intracoronary Ca2+ and epinephrine on the intracellular Ca2+ recirculation fraction (RF) and total Ca2+ handling in the left ventricle (LV) of the excised cross-circulated canine heart preparation. We analyzed LV postextrasystolic potentiation (PESP) following a spontaneous extrasystole that occurred sporadically under constant atrial pacing. All PESPs decayed in alternans and none decayed monotonically. We extracted an exponential decay component from the alternans PESP, determined its beat constant (taue), and calculated RF = exp(-1/taue). Increased intracoronary Ca2+ slightly increased taue and RF, but epinephrine did not change them, although both agents enhanced LV contractility 2-3 times. Neither Ca2+ nor epinephrine affected the sinusoidal decay of the alternans PESP. These results indicate that RF via the sarcoplasmic reticulum was slightly augmented by Ca2+, but not by epinephrine. We combined these RF data with LV Ca2+ handling O2 consumption data and obtained 40-110 micromol/kg as the total amount of Ca2+ handled in one cardiac cycle in the control and enhanced contractile states. These results indicate that this new LV-level approach seems to better the understanding of the Ca2+ mass dynamics responsible for the mechanoenergetics enhanced by inotropic interventions.

We briefly review that ventricular systolic pressure-volume area (PVA) can predict changes in myocardial O2 consumption (Vo2) associated with cardiac work production (positive work) and absorption (negative work). PVA represents the total mechanical energy of cardiac contraction as it is an integral of mechanical energy generated during systole in the cardiac chamber. We have shown that PVA linearly correlates with Vo2 under varied pre-and afterload conditions in the left ventricle of the excised cross-circulated canine heart preparation as well as other heart preparations of different species. PVA is the sum of external mechanical work (EW) and mechanical potential energy (PE) which is almost fully convertible to mechanical work without affecting Vo2. To compare the energetic effects of cardiac work production and absorption, we varied the timing of the servo pump motion relative to left ventricular (LV) contraction. When the pump fills the LV during diastole and sucks (allows ejection) during systole, cardiac work is produced by the heart, and hence EW > 0. When the pump fills the LV during systole and sucks during diastole, work is absorbed by the heart, and hence EW 0. It rotates clockwise when EW PE when EW > 0; PVA < PE when EW < 0. We found that Vo2 always linearly correlated with PVA regardless of the polarity of EW. Therefore, PVA is the unique determinant of Vo2 in a cardiac chamber in a stable contractility.