Long-term effects of cholesterol lowering and angiotensin-converting enzyme inhibition on coronary atherosclerosis: The Simvastatin/Enalapril Coronary Atherosclerosis Trial (SCAT).

BACKGROUND: This long-term, multicenter, randomized, double-blind, placebo-controlled, 2 x 2 factorial, angiographic trial evaluated the effects of cholesterol lowering and angiotensin-converting enzyme inhibition on coronary atherosclerosis in normocholesterolemic patients. METHODS AND RESULTS: There were a total of 460 patients: 230 received simvastatin and 230, a simvastatin placebo, and 229 received enalapril and 231, an enalapril placebo (some subjects received both drugs and some received a double placebo). Mean baseline measurements were as follows: cholesterol level, 5.20 mmol/L; triglyceride level, 1.82 mmol/L; HDL, 0.99 mmol/L; and LDL, 3.36 mmol/L. Average follow-up was 47.8 months. Changes in quantitative coronary angiographic measures between simvastatin and placebo, respectively, were as follows: mean diameters, -0.07 versus -0.14 mm (P:=0.004); minimum diameters, -0.09 versus -0.16 mm (P:=0. 0001); and percent diameter stenosis, 1.67% versus 3.83% (P:=0.0003). These benefits were not observed in patients on enalapril when compared with placebo. No additional benefits were seen in the group receiving both drugs. Simvastatin patients had less need for percutaneous transluminal coronary angioplasty (8 versus 21 events; P:=0.020), and fewer enalapril patients experienced the combined end point of death/myocardial infarction/stroke (16 versus 30; P:=0.043) than their respective placebo patients. CONCLUSIONS: This trial extends the observation of the beneficial angiographic effects of lipid-lowering therapy to normocholesterolemic patients. The implications of the neutral angiographic effects of angiotensin-converting enzyme inhibition are uncertain, but they deserve further investigation in light of the positive clinical benefits suggested here and seen elsewhere.

Electrocardiographic and ventriculographic recovery patterns in Q wave myocardial infarction.

To further define the capacity for recovery after acute phase electrical and mechanical injury in patients with Q wave myocardial infarction who were treated with standard measures, 120 lead body surface potential maps and radionuclide angiograms were recorded at day 5 before discharge and month 6 after infarction in 23 patients with a first infarction (12 anterior and 11 inferior by standard 12 lead electrocardiographic criteria). In addition to assessment of spatial changes in electrocardiographic and wall motion patterns, five quantitative variables were evaluated: minimal Q zone integral, sigma Q wave integral, maximal ST integral, left ventricular ejection fraction and left ventricular wall motion abnormality score. From day 5 to month 6 after infarction, the only change in the inferior infarction group was a gain in sigma Q wave (-91 +/- 40 mu V X s X 10(2) to -68 +/- 24 mu V X s X 10(2); p less than 0.05). In contrast, all variables improved over the same time period in the anterior infarction group: Q zone minimum, -34 +/- 20 to -24 +/- 13 mu V X s (p less than 0.05); sigma Q wave, -160 +/- 122 X 10(2) to -120 +/- 90 mu V X s X 10(2) (p less than 0.05); ST maximum, 44 +/- 19 to 18 +/- 9 mu V X s (p less than 0.01); ejection fraction, 54 +/- 7 to 63 +/- 17% (p less than 0.05); and wall motion score, 6 +/- 3 to 3 +/- 3 (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic body surface potential map patterns in left ventricular hypertrophy during PQRST.

Body surface potential maps were recorded from 117 thoracic sites and 3 limb electrodes in 173 normal subjects older than 30 years of age and 122 patients with clinically "pure" left ventricular (LV) hypertrophy. Typical LV hypertrophy map patterns were identified at successive instants during the PQRST waveform by removing from sequential LV hypertrophy maps the corresponding normal variability range at each electrode site. The presence in individual patients of 1 or more patterns typical in time and location of LV hypertrophy allowed retrospective assignment to the LV hypertrophy group. The most consistent discriminant patterns were excessive negative voltages in the anterior torso with reciprocal excess of positive voltages in the upper right chest during the second half of the P wave, excessive negative voltages in the lower right anterior torso at mid-QRS and excessive negative voltages in the left precordium with reciprocal excess of positive voltages in the upper right chest throughout ST-T. Best classification results were achieved with ST-T features, followed by features from the P wave, the QRS waveform and the PR segment. Cumulative use of ST-T and P features yielded a specificity of 94% with a sensitivity of 88%. Little improvement was obtained by the addition of QRS and PR information. The discriminant map criteria were applied to body surface potential maps from 169 new subjects (77 normal subjects ages 20 to 30 years and 92 patients with complicated LV hypertrophy). Little modification in specificity (93%) and sensitivity (90%) was observed. The performance of commonly used standard lead criteria was also tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of best electrocardiographic leads for diagnosing anterior and inferior myocardial infarction by statistical analysis of body surface potential maps.

In view of the increasing interest in quantifying and modifying the size of myocardial infarction (MI), it is important to look for clinically practical subsets of electrocardiographic leads that allow the earliest and most accurate diagnosis of the presence and electrocardiographic type of MI. A practical approach is described, taking advantage of the increased information content of body surface potential maps over standard electrocardiographic techniques for facilitating clinical use of body surface potential maps for such a purpose. Multivariate analysis was performed on 120-lead electrocardiographic data, simultaneously recorded in 236 normal subjects, 114 patients with anterior MI and 144 patients with inferior MI, using as features instantaneous voltages on time-normalized QRS and ST-T waveforms. Leads and features for optimal separation of normal subjects from, respectively, anterior MI and inferior MI patients were selected. Features measured on leads originating from the upper left precordial area, lower midthoracic region and the back correctly identified 97% of anterior MI patients, with a specificity of 95%; in patients with inferior MI, features obtained from leads located in the lower left back, left leg, right subclavicular area, upper dorsal region and lower right chest correctly classified 94% of the group, with specificity kept at 95%. Most features were measured in early and mid-QRS, although very potent discriminators were found in the late portion of the T wave.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of best electrocardiographic leads for diagnosing left ventricular hypertrophy by statistical analysis of body surface potential maps.

In view of the increased risk of cardiovascular mortality associated with left ventricular (LV) hypertrophy, early recognition and quantitation of LV hypertrophy are important clinical goals. The standard 12-lead electrocardiogram is the easiest and most widely used noninvasive method for the diagnosis of LV hypertrophy; unfortunately, the diagnostic accuracy of commonly used electrocardiographic criteria remains unsatisfactory. Body surface potential maps contain diagnostic information not present in conventional lead systems. The present investigation combines the increased information content of surface maps with the power of multivariate statistical techniques in order to identify practical subsets of electrocardiographic leads that would allow improved diagnosis of LV hypertrophy. Discriminant analysis was performed on 120-lead data simultaneously recorded in 250 normal subjects and 214 patients with LV hypertrophy using as features instantaneous voltages on time-normalized P, PR, QRS and ST-T waveforms as well as the duration of these waveforms. Leads and features for optimal separation of 173 normal subjects aged greater than or equal to 30 years from 122 patients with pure LV hypertrophy were selected. A total of 6 features from 5 torso sites accounted for a specificity of 97% and a sensitivity of 94%. The single most potent discriminator was the duration of the P wave; voltages were measured in mid and late P on leads located in the lower left parasternal area, the left precordial region and the upper right back, in mid-QRS on a lead positioned 10 cm below V1 and slightly before the peak of the T wave on a lead in the lower left flank.(ABSTRACT TRUNCATED AT 250 WORDS)

Improved prediction of left ventricular mass by regression analysis of body surface potential maps.

Electrocardiographic left ventricular (LV) hypertrophy involving ST-T abnormalities, in addition to high QRS voltages, is associated with increased risk of cardiovascular disease mortality. Unfortunately, conventional electrocardiographic criteria have limited utility in the quantitative assessment of LV hypertrophy. Body surface potential maps, which contain diagnostic information not present in commonly used lead systems, were recorded from 117 thoracic sites and 3 limb electrodes in 72 normal subjects and 84 patients with LV hypertrophy. Multiple regression analysis was performed separately for 54 women and 102 men on 120-lead data, using as features instantaneous voltages on time-normalized P, PR, QRS and ST-T waveforms. Leads and features for optimal prediction of echocardiographically determined LV mass were selected. A total of 6 features from 3 torso sites in men, and from the same 3 sites plus 2 others in women, yielded correlations between echocardiographic and electrocardiographic estimates of LV mass of 0.89 and 0.88, respectively. The standard errors of the estimate (SEE), or average errors in predicting LV mass from the regression equations, were 31 and 22 g, respectively. The single most potent predictor in both sexes was a mid-QRS voltage measured on a lead positioned 10 cm below V1; QRS duration, late QRS and early-to-mid T-wave amplitudes recorded in the lower left flank contributed significantly to the performance of both regression models. The optimal electrode sites for electrocardiographic prediction of LV mass were outside the conventional lead locations.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of best electrocardiographic leads for diagnosing myocardial infarction by statistical analysis of body surface potential maps.

This study describes a practical approach for the extraction of diagnostic information from body surface potential maps. Body surface potential map data from 361 subjects were used to identify optimal subsets of leads and features to distinguish 184 normal subjects from 177 patients with myocardial infarction (MI). Multivariate analysis was performed on 120-lead data, using as features instantaneous voltage measurements on time-normalized QRS and STT waveforms. Several areas on the map, most of which were located outside the precordial region, contained leads with important discriminant features; 2 of the 3 limb leads (aVR and aVF) also exhibited high diagnostic capability. A total of 6 features (mostly STT measurements) from 3 locations accounted for a specificity of 95% and a sensitivity of 95%; these were the right subclavicular area, the left posterior axillary region and the left leg. As a comparison, the same number of features from the standard 12-lead electrocardiogram yielded a sensitivity of 88% for a specificity of 95%. To investigate the repeatability of the results, the entire population was separated into a training set (100 normal subjects and 100 patients with MI) and a testing set (84 normal subjects and 77 patients with MI); computing a discriminant function on the training set and applying it to the testing set only moderately deteriorated the diagnostic classification. It is concluded that this approach achieves efficient information extraction from body surface potential maps for improved diagnostic classification.

Comparison of risk and patterns of practice in patients older and younger than 70 years with acute myocardial infarction in a two-year period (1987-1989)

To further evaluate contemporary risk and practice patterns in acute myocardial infarction (AMI), 402 consecutive patients with AMI between July 1, 1988, and June 30, 1989 were studied. The clinical investigations, medical therapy and outcome of patients aged greater than or equal to 70 years (n = 132; group 1) were compared with patients aged less than 70 years (n = 270; group 2). In group 1, 20% of patients had no typical cardiac pain versus 6% in group 2 (p less than 0.01). History of previous AMI, Q-wave AMI and peak creatine kinase were not different in the 2 groups. In-hospital mortality was markedly higher in group 1 (27%) than in group 2 (8%), p less than 0.01. Multivariate analysis revealed previous AMI, presentation without typical pain and age greater than or equal to 70 years to be independently associated with the greatest relative risk. Post-AMI exercise testing, ejection fraction calculations and coronary angiography were all performed less often (p less than 0.01); proven effective medical therapies, including thrombolysis, beta blockers, acetylsalicylic acid and nitrates were all used less frequently (p less than 0.01). The very high mortality and less aggressive management of elderly patients with AMI confirm similar data from our 1987 AMI patient cohort and other recently reported AMI patient outcome analyses. However, it remains uncertain why older patients with AMI are investigated and treated differently from younger patients. Further studies are warranted.

Qualitative and quantitative analysis of characteristic body surface potential map features in anterior and inferior myocardial infarction.

Body surface potential maps were recorded from 120 electrode sites in 236 normal subjects and 258 patients with initial evidence of either anterior myocardial infarction (MI) or inferior MI to identify characteristic map patterns in both groups. After time normalization, averaged map distributions were displayed at 18 equal time intervals during both QRS and ST-T waveforms from the normal, anterior MI and inferior MI groups. At each time instant, the 120-point averaged normal map was subtracted in turn from the corresponding anterior and inferior MI maps; the resulting differences at each electrode site were divided by the pooled standard deviation and the obtained values (discriminant indexes), plotted as contour lines with 1 standard deviation increments, producing discriminant maps for each bi-group comparison. The most consistent discriminant patterns in 114 patients with anterior MI were observed in early QRS in the upper left anterior chest where abnormal negative voltages reflected loss of electric potentials while reciprocal changes were noticed in the lower back; by mid-QRS, both distributions had moved jointly and vertically, the former in the lower torso on the midsternal line, the latter in the upper back. In 144 patients with inferior MI, abnormal positive distributions were observed in early QRS in the upper back, followed later by excessive negative voltages in the inferior right anterior chest; at mid-QRS, both distributions had migrated horizontally, the former proceeding toward the upper anterior torso, the latter to the lower left dorsal area.(ABSTRACT TRUNCATED AT 250 WORDS)

Body surface potential maps with low-level exercise in isolated left anterior descending coronary artery disease.

One hundred and twenty-lead body surface potential maps (BSPMs) were recorded at rest, at immediate cessation of exercise and after 1 (early) and 5 minutes (late) of recovery in 14 patients with isolated, critical, left anterior descending (LAD) coronary artery stenosis. Exercise endpoints, at an average peak rate of 98 +/- 13, were usual pain worsening in 13 LAD patients, and diagnostic ST depression in lead V5 in 1 patient. Twelve patients also had positive thallium scans. BSPMs were also recorded in 8 normal subjects who exercised to peak heart rates similar to those of the LAD subjects. Spatially, there were similar exercise changes in QRS and ST-segment integral patterns over the precordium and inferior torso in both groups. These were transient in the control group but persisted to late recovery in the LAD group, particularly for ST integral. Quantitatively, multivariate analysis revealed significant temporal differences between the 2 groups. However, the only independent BSPM variable was the sum of ST integral decrease, averaging --2,323 +/- 1,809 microV.s for normal patients between rest and immediate cessation of exercise, compared with -3,828 +/- 2,329 microV.s for the LAD patients (p less than 0.05). Late recovery minus rest difference averaged -1,264 +/- 1,080 microV.s for normal subjects and -2,575 +/- 1,844 microV.s for LAD patients (p less than 0.01). To control for the physiologic changes of exercise, the ST integral temporal differential maps of the normal subjects were subtracted from those of the LAD patients and the sum of negative intergroup differences was assumed to reflect only ischemia. Correlation of ST integral ischemia values at immediate cessation of exercise and late recovery was high (r = 0.88); however, intertechnique correlations of the BSPM variables with quantitative angiographic scores and thallium perfusion scan scores revealed generally low r values (range 0 to 0.52). These data demonstrate that ischemic repolarization changes are detectable and quantifiable by BSPM at low levels of cardiac stress in patients with 1-vessel disease when the usual electrocardiographic criteria of myocardial ischemia are frequently absent. The data further suggest that ST integral changes reflective of myocardial ischemia persist well after the exercise recovery period and that they are complementary to, rather than substitutionary for, other indirect measures of myocardial ischemia.

Non-Q-wave acute myocardial infarction: body surface potential map and ventriculographic patterns.

Day 5 body surface map and radionuclide angiographic patterns were compared among 56 patients with first non-Q-wave or Q-wave acute myocardial infarction (AMI). Three radionuclide angiographic patterns were recognized in patients with non-Q infarction: no wall motion abnormalities (n = 8), single-segment wall motion abnormalities (n = 10) and multiple-segment wall motion abnormalities (n = 9). In contrast, only 2 radionuclide angiographic patterns were identified in patients with Q-wave infarction: multiple-segment wall motion abnormalities (n = 25) and single-segment wall motion abnormalities (n = 4). The Q-wave distributions of 14 of 18 patients with non-Q infarction with 0 or 1 wall motion abnormalities were normal; 2 patients had "missed" anterior; 1 patient had inferior; and 1 had posterior AMI patterns. Of 9 patients with non-Q infarction who had multiple-segment wall motion abnormalities, 8 had infarct Q waves on the posterior torso. Q-wave patterns in patients with anterior (n = 17) and inferior (n = 12) Q-wave infarctions were typical and homogeneous for each group. Quantitative analysis of minimum Q-zone integral, sigma Q-wave integrals, ST-integral maximum, wall motion abnormality score and ejection fraction revealed no differences between patients with non-Q-wave and those with inferior Q-wave infarction. In contrast, patients with anterior AMI had significantly more abnormal values of all variables than either of the other groups. Overall, the data support the concept of non-Q-wave AMI as a distinct, if heterogeneous, pathophysiologic entity.(ABSTRACT TRUNCATED AT 250 WORDS)

Frequent ventricular ectopic activity without underlying cardiac disease: analysis of 45 subjects.

Forty-five subjects, aged 2 weeks to 62 years, who presented with frequent (greater than 100/day) ventricular ectopic beats (VEBs) and without evidence of underlying cardiac disease were studied. The spectrum of ventricular dysrhythmia was assessed by 24-hour ambulatory electrocardiography and exercise tolerance test. Sinus rhythm was the prevailing rhythm in all subjects. VEB frequency averaged 444 +/- 454 per hour (range 0 to 1,863) over the 24-hour monitoring period and was not significantly different during waking or sleeping periods. There was no simple correlation of VEB frequency with prevailing sinus rate (r = -0.0006; p = not significant [NS]). The prevalence of complex VEBs (multiform, R-on-T and repetitive) was relatively high (18 of 45 patients), and was equally distributed about the median VEB frequency of 314 VEBs/hour (7 of 18 versus 11 of 18; NS). Of the 43 subjects who had exercise tests, 37 had VEBs during the preexercise rest phase, compared with only 11 at peak exercise (p less than 0.0001). To assess the short-term natural history of the VEBs, 27 subjects had repeat clinical examinations and 24-hour electrocardiograms at a mean interval of 8 months. All remained well. Although there was considerable individual temporal variability of VEB frequency in this subgroup, there was no significant change in group mean values (415 +/- 409 VEBs/hour initially versus 401 +/- 383 VEBs/hour at follow-up study; NS). The relative temporal constancy of VEB frequency in the group as a whole was also reflected in a high linear correlation of VEB frequency at initial and follow-up studies (r = 0.816; p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac rhythm, rate and ventricular repolarization properties in infants at risk for sudden infant death syndrome: comparison with age- and sex-matched control infants.

Using 24-hour ambulatory electrocardiographic recordings and 120-lead body surface potential maps, prevailing cardiac rate and rhythm, incidence and frequency of dysrhythm and rate and pattern of ventricular repolarization at the body surface were compared in 17 infants at risk for sudden infant death syndrome (SIDS) and 17 age- and sex-matched control subjects. Sinus rhythm was the prevailing rhythm in both study groups and there were no intergroup differences in average overall awake or asleep sinus rates, nor in temporal variability of sinus rate. Atrial and ventricular ectopic activity were equally uncommon in both study groups. Although there were smooth and bipolar body surface distributions of ST-T and QRST time integrals in both study groups, the average rate of ventricular repolarization (QTc), measured from the 12-lead electrocardiogram, 120-lead body surface potential maps and 24-hour electrocardiography, was consistently shorter in the at-risk group than in the control group. However, temporal variability of QTc was not different between the 2 groups. Thus, significant cardiac dysrhythm and QT prolongation are not found in infants at increased risk for SIDS. Rather, there is an abbreviated ventricular repolarization interval in at-risk infants. In combination with the findings of intergroup similarity of average sinus rate and temporal variability of sinus rate and ventricular repolarization rate, the data suggest a subtle, constant difference in cardiac autonomic activity, most likely an increase in sympathetic tone, in at-risk subjects. The role of this altered cardiac autonomic activity in the causation of SIDS remains undetermined.

Mass ammonia inhalation.

The clinical, roentgenographic and laboratory findings, their relationship to each other and to the subsequent hospital course are reported for 14 victims of gaseous ammonia inhalation. Initial physical examination enabled differentiation of a mildly affected from a moderately affected group, but patients in both groups responded well to conservative medical management.

Dilated right ventricular cardiomyopathy: Uhl's disease.

Uhl's disease is a rare disorder originally described in 1952 in an infant with severe diffuse right ventricular dysfunction with total absence of the myocardium. Uhl considered the disease to be congenital in origin. We report a patient with severe dilated congestive cardiomyopathy limited to the right ventricle but apparently developing in adulthood.

High-dose caffeine and cardiac rate and rhythm in normal subjects.

In a previous 24-hour study of the electrophysiologic effects of moderate dose caffeine (1 mg/kg body weight/half-life), we found a significant (p less than 0.01) increase in ventricular ectopic beat (VEB) frequency among 18 patients with preexisting primary ventricular dysrhythm (mean 207 +/- 350 VEBs/hour, no caffeine, versus 307 +/- 414 VEBs/hour, caffeine). We also found a statistically insignificant (NS) increase in the incidence of infrequent VEBs in 18 normal control subjects (four of 18, no caffeine vs nine of 18 caffeine). Because of the high risk of beta-error among the previously-studied normal control subjects, we tested another group of 34 normal subjects, 15 males and 19 females with a mean age of 31 years (range 21 to 49 years), using a higher dose of caffeine. All subjects abstained from caffeine for 72 hours and had a control 24-hour Holter ECG recorded between hours 48 and 72. Caffeine half-life was calculated for each subject and caffeine was then ingested at 1 mg/kg every 0.5 half-life during all waking hours. A 24-hour Holter test was recorded, beginning just prior to the second caffeine dose. It was concluded that in normal adults, even high-dose caffeine does not affect prevailing cardiac rhythm and rate, and moreover, does not cause clinically significant ventricular or supraventricular dysrhythm.

In vivo right heart thrombus. Precursor of life-threatening pulmonary embolism.

This report describes three cases of massive mobile right heart thrombus and reviews the available literature to better define the pathophysiology, natural history and most appropriate therapy of the syndrome. The clinical presentation of most patients has been severe cardiopulmonary dysfunction and the diagnosis has been made by echocardiographic study. The most likely source of these cardiac thrombi is the large systemic veins. The associated mortality risk is very high. Therapy has, heretofore, been individualized. Embolectomy has been most favored, with a survival rate of 80 percent. The role of thrombolytic therapy remains to be delineated. Therapy should, however, be initiated rapidly because of the precipitous nature of the mortality risk.

Cardiac function at rest and with exercise in the chronic fatigue syndrome.

To evaluate a possible cardiac pathophysiology of the chronic fatigue syndrome, we compared the resting cardiac function and exercise performance of 41 patients to those of an age-matched and sex-matched normal control group. Persistent fatigue following an acute apparently viral illness was the major complaint of all patients; none had specific cardiac symptoms nor abnormal physical findings. Electrocardiographic spatial patterns were normal in the patients, and there were no differences in the body surface sum of positive T-wave integrals between the patients (240 microV.x 10(2) +/- 107 microV.s x10(2)) and control (244 microV.x 10(2) +/- 108 microV.s x 10(2) subjects. Twenty-four hour ambulatory ECGs revealed no differences in sinus rates and incidences of ventricular dysrhythmias in the two populations. Left ventricular dimensions and systolic fractional shortening values were also similar in both groups; moreover none of the patients had segmental wall motion abnormalities. On graded exercise testing, 20 of 32 normal subjects achieved target (85 percent of age-maximum) heart rates, compared to four of 31 patients (p less than 0.001). The duration of exercise averaged 12 +/- 4 minutes for the normal subjects and 9+/- 4 minutes for the patients (p less than 0.01). The temporal profile of exercise heart rates was dissimilar in the two groups, with patients' rates consistently and progressively less than those of normal subjects. Peak heart rate averaged 152 +/- 16 beats per minute for the normal group vs 124 +/- 19 beats per minute for the patients (p less than 0.0001); in age-related terms, respectively, 82 +/- 6 percent of the maximum heart rate vs 66 +/- 10 percent (p less than 0.0001). Thus, patients with chronic fatigue syndrome have normal resting cardiac function but a markedly abbreviated exercise capacity characterized by slow acceleration of heart rate and fatigue of exercising muscles long before peak heart rate is achieved.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of caffeine on cardiac rate, rhythm, and ventricular repolarization. Analysis of 18 normal subjects and 18 patients with primary ventricular dysrhythmia.

To determine clinical electrophysiologic effects of a moderate dose of caffeine, we compared prevailing cardiac rhythm and rate, the prevalence and frequency of ventricular dysrhythmia, and Q-T intervals in two populations over an initial 24-hour caffeine-free period and a subsequent 24-hour period in which caffeine was ingested in a dosage of 1 mg/kg of body weight at intervals of one half-life during waking hours. Group 1 was composed of 18 clinically normal subjects; group 2 was 18 subjects with frequent ventricular ectopic beats (VEBs) and no (n = 16) or minor (n = 2) cardiac disease. Sinus rhythm was the prevailing rhythm in all subjects at all times. For group 1, the mean sinus rate during the caffeine-free period was 77 +/- 10 beats per minute, compared to 73 +/- 9 beats per minute during the period of caffeine ingestion (not significant). Similarly, for group 2, the average sinus rate during the caffeine-free period was 76 +/- 11 beats per minute, not significantly different from the average sinus rate during the test period, 76 +/- 10 beats per minute. During abstention from caffeine, four of 18 subjects in group 1 had infrequent (less than 1/hr) VEBs, compared to nine of 18 during caffeine ingestion (not significant). In group 2, some 16 of the 18 subjects had VEBs during the caffeine-free period, with the frequencies varying from less than one VEB per hour to 1,449 VEBs per hour. During the test period, 14 of the 18 subjects in group 2 increased their VEB frequency, and the group's mean frequency rose from 207 +/- 350 VEBs per hour (control period) to 307 +/- 414 VEBs per hour (test period) (p less than 0.01). The Q-T interval in group 1, measured as the corrected Q-T interval (Q-Tc), averaged 0.430 +/- 0.027 during the caffeine-free period, not significantly different from the test period (0.425 +/- 0.019). The comparable Q-Tc values for group 2 were 0.424 +/- 0.018 during the caffeine-free period and 0.433 +/- 0.025 for the period of caffeine ingestion (not significant).(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiac effects of common viral illnesses.

We compared the clinical, electrocardiographic and echocardiographic findings of 32 patients during the acute and recuperative phases of viral illness with similar data from a healthy age- and sex-matched normal control group. During the acute phase, no patient had cardiac symptoms and none had clinical evidence of left ventricular or valvular dysfunction, nor pericarditis. Electrocardiograms revealed no differences in mean sinus rate or ectopic dysrhythm between the two groups. Spatial 12- and 120-lead body surface electrocardiographic patterns were normal in 30 patients; two others had nonspecific T wave abnormalities. There were no differences in echo-determined left ventricular cavity size or systolic shortening fraction between the two groups. Three patients had segmental ventricular hypokinesis; 17 patients had small pericardial effusions. Data herein suggest effects on myocardial electrical and mechanical function in patients with viral illness. It may be prudent for such patients to minimize cardiac stress during illness.