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The authors describe a method to account for patient-to-patient variability in electrocardiographic data. The method yielded criteria for healed inferior myocardial infarction with diagnostic performances better than those of traditional electrocardiographic parameters.

The ratio of the 30th to the 15th cardiac cycle duration on an electrocardiogram (30:15 ratio) immediately after active standing from the supine position has been used as one of the markers of baroreflex function. A ratio of < or = 1.0 has been suggested to indicate baroreflex dysfunction. Blood pressure (BP) changes were measured and the 30:15 ratio was calculated after standing and during 45-degree passive head-up tilt from the supine position in 10 nondiabetic men (mean age +/- SE 70.1 +/- 1.05 years, and BP < 150/90 mm Hg). After tilt the decrease in systolic BP (from 132 +/- 4.8 to 117 +/- 6.3 mm Hg; p < 0.001) appeared to be larger than that after standing (from 132 +/- 4.6 to 123 +/- 5.8 mm Hg; p < 0.01), whereas the 30:15 ratios were 0.965 +/- 0.006 and 0.970 +/- 0.014, respectively, which suggested baroreflex dysfunction. Although the mean of the 2 ratios did not differ, the variance appeared to be less during tilting than after standing. Thus, the 45-degree passive head-up tilt appeared to be a better and more uniform inducer of orthostatic stress than active standing. Therefore, 45-degree head-up tilt was used in a group of 10 nondiabetic male patients (aged 70 +/- 1.46 years) with isolated systolic hypertension (systolic BP > 160 mm Hg, diastolic BP of < 90 mm Hg) to assess their baroreflex function. Upon tilting, their systolic BP decreased from 190 +/- 5.5 to 179 +/- 5.8 mm Hg (p < 0.05) and their 30:15 ratio was 0.985 +/- 0.011.(ABSTRACT TRUNCATED AT 250 WORDS)

The hemodynamic effects of orthostatic stress in elderly subjects with systolic hypertension were studied before and after long-term hydrochlorothiazide therapy (50 mg daily). Sixteen nondiabetic men aged 70 +/- 1 (SE) years participated in the study initially, and 12 completed 1 year of therapy. Patients underwent 45 degrees head-up incline on a tilt table before, after 1 month and after 1 year of therapy. Hemodynamic variables were measured in the following situations: (1) the supine position, (2) immediately after completion of passive 45 degrees head-up position at 0 minute, (3) at 15 minutes in the tilted state while patients performed intermittent foot movements to minimize gravitational pooling and simulate the standing position outside the laboratory, and (4) after returning to the supine position. Systolic and diastolic blood pressure (BP) decreased significantly after 1 month of therapy, and this reduction was maintained up to 1 year in all aforementioned body positions, with the exception of diastolic BP at 0 minute of tilt, which was significant at 1 year only. Before therapy was begun, there was a significant reduction in systolic BP immediately after completion of tilting; however, this was statistically insignificant both at 1 month and 1 year of therapy. Thus, the data may help dispel the concern of exacerbating the hypotensive response to orthostatic stress in patients with systolic hypertension after long-term thiazide diuretic therapy.

New electrocardiographic (ECG) criteria for the diagnosis of left anterior hemiblock are proposed. The proposed criteria are based upon the relation between portions of the vectorcardiographic (VCG) QRS loop in the frontal plane and the corresponding portions of the ECG QRS complexes recorded by the limb leads. The application of the proposed criteria requires that the tracings be obtained with 3-channel ECG machines so that the temporal relation between the QRS complexes in simultaneously recorded limb leads can be inspected. This type of analysis of the electrocardiogram permits prediction of features of the VCG QRS loop that are important for the diagnosis of left anterior hemiblock. The proposed ECG criteria for the diagnosis of left anterior hemiblock are (1) the QRS complexes in leads aVR and aVL each end in an R wave (terminal R wave), and (2) the peak of the terminal R wave in lead aVR occurs later than the peak of the terminal R wave in lead aVL. The sensitivity and specificity of the proposed criteria were empirically evaluated using series of electrocardiograms obtained under clinical circumstances during which the occurrence of left anterior hemiblock was, respectively, likely and unlikely. The performance of the proposed criteria was statistically superior to that of 2 sets of frontal plane QRS axis criteria.

A scalar electrocardiogram (ECG), orthogonal ECG and vectorcardiogram (VCG) were recorded in 46 normal persons, 38 patients with inferior myocardial infarction (MI) and 22 patients with anterior MI proved at cardiac catheterization. The diagnostic information provided by the scalar ECG, orthogonal ECG and VCG was quantitatively analyzed and the optimal criteria for diagnosing inferior and anterior MI exhibited by each method were identified. The optimal scalar electrocardiographic, orthogonal electrocardiographic and vectorcardiographic criteria, respectively, are: For inferior MI: initial superior duration in lead aVF greater than 30 ms (sensitivity 63%, specificity 100%), superior/inferior amplitude ratio in lead Y greater than or equal to 0.2 (sensitivity 63%, specificity 96%), initial superior duration greater than 29 ms or initial superior distance greater than 0.4 mV in the frontal plane loop (sensitivity 68%, specificity 100%). For anterior MI: initial anterior duration in lead V2 less than 20 ms or initial anterior duration in lead V3 less than 25 ms (sensitivity 91%, specificity 100%), anterior/posterior duration ratio in lead Z less than 0.3 (sensitivity 73%, specificity 98%), initial anterior duration less than 15 ms in the transverse plane loop (sensitivity 64%, specificity 98%). There were no significant differences among the performances of the optimal scalar ECG, orthogonal ECG and the VCG for diagnosing inferior MI. However, the performance of the optimal scalar ECG was superior to that of the optimal orthogonal ECG and the optimal VCG for diagnosing anterior MI (chi-square = 5.20, p less than 0.02 and chi-square = 7.14, p greater than 0.01, respectively).

The scalar electrocardiograms of 64 patients with inferior wall myocardial infarction (MI) and 87 normal subjects were quantitatively analyzed to determine the respective contributions of the initial and terminal portions of the QRS to the diagnosis of inferior MI. Of the 10 best individual electrocardiographic criteria for inferior MI, 7 were Q-wave criteria and 3 were criteria that consisted of delayed termination of the QRS in leads II or III. Combining the best terminal QRS criterion (the QRS in lead III ending at least 20 ms later than the QRS in lead I) with the 7 best Q-wave criteria and the best Q-wave criterion (Q wave 40 ms or longer in lead aVF) with the 3 best terminal QRS criteria, resulted in criteria with better sensitivities and overall diagnostic performances than those of the individual criteria. Analyzing the vectorcardiograms that were also available in 26 of the patients with inferior MI and 34 of the normal subjects showed that the delayed inscription of the end of the QRS in leads II and III in patients with inferior MI is due to redirection of the terminal forces of ventricular depolarization. The terminal portions of the QRS complexes in the limb leads, considered both alone and in conjunction with traditional measurements of Q waves, contain information that is useful for diagnosing inferior MI.

Twenty-four men, mean age 63 +/- 1.7 years, with systemic systolic hypertension were studied before and after 1 month of therapy with oral hydrochlorothiazide, 50 mg/day. The control mean plasma volume was 2,664 +/- 96 ml, cardiac index 3.9 +/- 0.2 liters/min/m2, stroke volume index 52 +/- 2 ml/beat/m2, systemic vascular resistance 1,351 +/- 80 dynes s cm-5, plasma aldosterone 8.6 +/- 1.0 ng/dl and 24-hour urinary excretion of metanephrines 0.371 +/- 0.044 mg. On renin-sodium profiling in 23 patients, 12 were classified into a normal group and 11 into a low-renin group; none had high renin values. Based on multiple regression analysis, the 24-hour urinary excretion of total metanephrines appeared to be the single most important factor explaining 28% of the variability in systolic blood pressure (BP). After therapy with oral hydrochlorothiazide, the elevated systolic BP decreased (p less than 0.0001) and diastolic BP decreased (p less than 0.005), with concomitant reduction in systemic vascular resistance (p less than 0.03). Patients in both the normal- and low-renin groups had normal plasma volume and responded similarly to thiazide diuretic therapy, without symptomatic side effects.

A systematic evaluation of a large number of electrocardiographic (ECG) variables that might be useful for diagnosing anterior myocardial infarction (MI) is reported. Previous anterior MI was shown to be present or absent by cardiac catheterization in 199 patients. The best discriminator between cases and noncases of anterior MI in most patients is the presence of a Q wave of any magnitude or an initial R wave less than 20 ms in lead V2. In patients with ECG evidence of associated left ventricular or type C right ventricular enlargement, the more stringent criterion of a Q wave of any magnitude in lead V2 yielded the optimal combination of sensitivity and specificity for diagnosing anterior MI. The diagnostic performance of the proposed criteria for anterior MI is superior to that of more traditional criteria that use measurements of the absolute and relative amplitudes of precordial R waves.

As many as 30% of patients with chest pain symptoms who are referred for arteriography are found to have normal coronary arteries. Research has shown that patients with anginal symptoms and normal coronary arteries score higher on neuroticism measurements (anxiety, depression and somatic concerns) at the time of catheterization than patients with anginal symptoms who have coronary artery disease. Research examining the cardiac course of chest pain patients with normal coronary arteries indicates that this is a nonprogressive disorder. Although follow-up studies of these patients report continued chest pain and diminished physical activity, these studies have ignored the psychologic status of the patients. Thus, it is not known whether their higher neuroticism scores at the time of catheterization persist following angiography or whether such elevated indexes of neuroticism are transient phenomena associated with precatheterization anticipatory stress. The present study examined 48 Veterans Administration Medical Center patients: 24 with anginal symptoms and normal coronary arteries and 24 with documented coronary artery disease. The patients completed a structured clinical interview and a set of psychologic inventories on the day before catheterization and 1 year later. The findings established continued high neuroticism scores among patients with anginal symptoms only and supported the findings of other investigators regarding continuing chest pain and restricted physical activity. The knowledge alone of benign coronary artery status resulted in virtually no change in the psychosocial status of these patients. Alternative treatment methods are discussed.

The vectorcardiograms of 41 patients with angiographically proved inferior myocardial infarction (MI) and 51 normal subjects were analyzed to determine whether it is the time (in milliseconds) or the distance (in millivolts) of the initial superiority directed forces of ventricular depolarization that is increased more by inferior MI, and whether parameters derived from both the initial superior time and distance can be used to detect inferior MI. The 10 best individual and the 10 best paired criteria for inferior MI involve superior distance, either alone or used in the calculation of average velocity (in volts per second), and the product of initial superior time and distance (in millivolts per second). The 2 best individual criteria for inferior MI are: inferior velocity more than 0.0065 V/s (sensitivity 71%, specificity 100%) and superior distance more than 0.39 mV (sensitivity 68%, specificity 100%). These diagnostic performances are superior to those of the best criterion that involves only the duration of the initial superior forces, i.e., initial superior time longer than 28 ms (sensitivity 49%, specificity 98%) (chi 2 = 8.42, p less than 0.005 and chi 2 = 6.31, p less than 0.025, respectively). Initial superior distance and parameters calculated from both initial superior distance and time are better vectorcardiographic criteria for inferior MI than are criteria that involve only initial superior time.

To determine the diagnostic significance for coronary artery disease of abnormally large Q waves in leads I, aVL, V5 and V6--the "lateral" electrocardiographic leads--the electrocardiograms of 240 patients who had undergone cardiac catheterization were studied. First, the electrocardiograms of 99 subjects proved normal by cardiac catheterization (group 1) were studied to determine the values of the durations of Q waves in leads I, aVL, V5 and V6 that should be exceeded to be considered abnormal. These values were 30, 30, 20 and 25 ms, respectively. Then, 67 patients were identified who had abnormal Q waves in at least 1 of these leads (group 2) and 74 patients with at least 1 angiographic abnormality but without abnormal Q waves in any of these leads (group 3). Group 2 had generally more extensive left ventricular disease and a higher prevalence of anterior, inferior and apical healed myocardial infarction (MI) than group 3. However, compared with group 3, group 2 had lower prevalences of significant narrowing of the coronary arteries that supply the left ventricular lateral wall. Within group 2, abnormal Q waves in leads I and aVL (traditionally designated high lateral MI) were associated with anterior as well as apical MI, and abnormal Q waves in leads V5 and V6 (traditionally designated anterolateral MI) were associated with inferior as well as apical MI. Thus, abnormal Q waves in leads I, aVL, V5 and V6 tend to reflect apical rather than lateral MI and the term anterolateral MI is especially misleading.

New electrocardiographic (ECG) criteria for diagnosing the combination of inferior myocardial infarction and left anterior hemiblock are proposed. The proposed criteria are based upon the relations between portions of the vectorcardiographic QRS loop in the frontal plane and the corresponding portions of the QRS complexes recorded by the limb leads. The application of the proposed criteria requires that the tracings be obtained with 3-channel ECG machines. The proposed criteria for the diagnosis of inferior myocardial infarction and left anterior hemiblock are as follows: (1) leads aVR and aVL both end in R waves, with the peak of the terminal R wave in lead aVR occurring later than the peak of the terminal R wave in lead aVL, and (2) a Q wave of any magnitude is present in lead II. The performance of the proposed criteria was superior to that of 10 combinations of traditional ECG criteria for inferior myocardial infarction and left anterior hemiblock.