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The cardiopneumogram has been reinvestigated as an index of stroke volume and cardiac output in anaesthetized dogs. Using a water-filled oesophageal balloon to calibrate the system good correlations have been found between the values derived from dye dilution and the indices obtained from the cardiopneumogram.
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One hundred and one consecutive post-myocardial infarction (MI) patients were investigated with 24-h long-term ECG registration (LTER), exercise test and radionuclide angiocardiography (RNA) within one month of the MI and after six and 12 months. Patients with low left ventricular ejection fraction (LVEF) or a high value in a quantified phase analysis (Phase SD) were found to have frequent ventricular arrhythmia and high Lown class. Significant correlations between LVEF or phase SD and the number of ventricular arrhythmias or Lown class were found (P less than 0.05). Frequent ventricular arrhythmias and high Lown class were also found in patients with inverse left ventricular wall movement at RNA. Prolonged QTc was found in patients with frequent ventricular arrhythmias. These connections were found at all three investigations during the follow-up year. A significant correlation was not observed between ventricular arrhythmias and exercise capacity, NYHA grouping, ST depression in an exercise test or symptoms of angina pectoris. More than 300 ventricular premature complexes (VPC) per 24 h was found to predict death during the follow-up year as was LVEF less than 30%; complex arrhythmia (i.e., the patient being in Lown classes 3-5) being the only factor to predict repeat-MI during the follow-up year. It is concluded, that ventricular arrhythmias in the post-MI patient reflect the left ventricular performance. Both LVEF and arrhythmias contribute univariately to the risk of death during the first year after an MI. Whether they both carry independent prognostic information for death must be studied in future larger trials.
Factor analysis of dynamic structures (FADS) can automatically provide "physiological" factors related to anatomical structures that have different temporal behavior, even if these structures overlap; it also yields images corresponding to the factors' spatial distributions. In normal patients, two significant cardiac factors, corresponding to the atria and the ventricles, may be extracted. A third significant factor can be obtained when additional dynamic structures exist. However, the method does not provide an estimate of the background. It becomes part of the factors, but it does not modify their shapes. FADS has been applied to 45 gated cardiac studies. Results obtained by FADS were compared with those obtained from the amplitude and the phase of first-harmonic Fourier analysis (FA). The joint results were compared with the final diagnosis, established by real-time echocardiography and/or ventriculography. In normal patients, good agreement was obtained between the two approaches. On the whole set of patients, FADS was significantly better than FA (by sign test: p less than 5%).
Examination of 84 essentially healthy men, aged 19 to 34 years, by the rebreathing method showed that in various test subjects the reserve time prior to decompensation was in the range 5 to 9 min. A certain change was seen 1-2 min before termination of the test due to acute respiratory failure. This change included an increase in the minute respiration volume above 40 1/min and its relative increment by 10 1/min or over when compared to the preceding minute. The test time varied from 4 to 8 min. Analysis of the data using the cardiorespiratory index which is equal to the product of heart rate by systolic arterial pressure divided by the minute respiration volume helped to discriminate test subjects with satisfactory, good and very good tolerance of the rebreathing test.
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We examined serial exercise test performance in children with congenital aortic stenosis (AS) treated surgically compared to that of nonoperated children with mild to moderate AS. Maximal treadmill exercise data were assessed in 21 children 5.5 +/- 3.8 years after aortic valve (AO) surgery. Patients had undergone the Ross procedure (n = 6) or previous aortic valvotomy, balloon valvuloplasty, or neonatal aortic valvotomy (n = 15). Follow-up treadmill tests were conducted 3.7 +/- 2.8 years later. Data were compared to those of 19 nonoperated AS patients (mean gradient by echocardiogram <50 mmHg). These patients were exercised 3.6 +/- 3.2 years apart. Endurance time, heart rate, systemic blood pressure, and electrocardiogram were compared as repeated measures between tests and to age- and sex-matched normative data. Postsurgical children with AS had normal endurance times despite low peak heart rates on the initial test, and they maintained endurance over time. Nonoperated children with mean AO gradients <50 mmHg also had normal endurance times on the initial test but increased endurance over 3.6 years. Children with operated and nonoperated AS were able to reach or exceed normal endurance times, which may make it difficult to achieve compliance to imposed activity restrictions in this population.
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Two hundred consecutive patients with a history of chest pain undergoing cardiac catheterization, coronary angiography and atrial pacing have been analyzed to assess the clinical significance of Mobitz I atrioventricular (A-V) block developing with the stress of atrial pacing. Of 160 patients with coronary artery disease, 26 (16%) developed Mobitz I A-V block at rates below 140 beats/min. Eighteen of these 26 patients (69%) had electrocardiographic evidence of old inferior wall myocardial infarction, compared to only 34 of the remaining 134 patients (29%) (P = less than 0.01). During the mean follow-up of 29.5 months (range 18-50 months) none of the 26 patients has developed spontaneous second or third degree A-V block. Twenty-three of the 26 patients had an exercise test within one week of the pacing study. No A-V block was noticed during or immediately following exercise, although the mean heart rate attained during exercise was higher than the mean pacing rate at which the A-V block occurred (136 +/- 5 vs 122 +/- 3, P = less than 0.01). Eighteen of these 23 achieved heart rates equal to or higher than the pacing rate at which A-V block developed. Nineteen (83%) shortened their P-R interval during exercise and 4 (17%) did not change the P-R length. Although atrial pacing-induced Mobitz I A-V block may indicate a latent A-V nodal conduction abnormality in some cases, its demonstration does not necessarily predict the occurrence of spontaneous advanced A-V block. Exercise should not be restricted in these patients on the basis of such a finding during a pacing study.
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UNLABELLED: Between 1971 and 1980 uniform ventricular extrasystoles, classified as benign, were noticed in 47 children with normal hearts. After a mean observation period of 4.4 years 27 of these children, mean age 10.5 years, could be reexamined. This involved physical examination followed by resting and exercise ECG, 24-hour continuous ECG and echocardiography. Of the 27 children, 18 still had extrasystoles having the same morphological characteristics and identical behaviour under exercise as those seen on first examination. Nine children were free of extrasystoles in all ECG examinations. In none of the 27 children were there any complaints between the first and the second examination or signs of degeneration of the extrasystoles into threatening dysrhythmias. CONCLUSION: Uniform extrasystoles disappearing or decreasing on exercise in otherwise healthy children require no treatment even when occurring frequently and persisting over years.
Blood pressure, heart rate, and echocardiographic parameters of left ventricular size and shortening were measured both under baseline conditions and during handgrip exercise (50% maximum handgrip effort held to fatigue) in 20 normal women (20 through 29 years of age). As a group, there was a significant increase in heart rate (72 +/- 10 vs 83 +/- 12; P less than .001), systolic blood pressure (111 +/- 8 vs 133 +/- 14 mm Hg; P less than .001), diastolic blood pressure (67 +/- 8 vs 89 +/- 12 mm Hg; P less than .001), and calculated cardiac output (4.3 +/- 1.5 vs 5.2 +/- 1.7 liters/minute; P less than .005). There was no significant change in left ventricular internal dimension in diastole or systole, shortening fraction, or calculated stroke volume. The average group response of an increase in cardiac output secondary to an increase in heart rate is similar to that of male subjects in their second decade. Individual variability in responses was of specific interest since only three of the 20 women demonstrated a totally characteristic response to handgrip exercise. Handgrip exercise in young women may not provide a uniformly characteristic response from which to predict hemodynamic changes in a given individual and may lead to clinical misinterpretation if appropriate caution is not used.
The influence of the interval between beats on myocardial contractility was examined in conscious dogs previously instrumented with a left ventricular micromanometer and ultrasonic crystals measuring left ventricular major and minor diameters and parietal wall thickness during control state and after inflation of an aortic cuff. Ventricular contraction was measured during variations of diastolic intervals (DI) produced by respiratory arrhythmia or atrial pacing. During control before aortic stenosis, minor equator shortening (% delta L) increased slightly after long (L) DI compared with short (S) DI with a corresponding decrease of end-systolic stress. During aortic stenosis, LDI were associated with a significant increase of % delta L compared with SDI although end-systolic stress was larger. Thus end-systolic stress-diameter relations were not modified during control but they were significantly shifted to the left after LDI during aortic stenosis. Inotropic state is thus increased after LDI during acute pressure overload but not during control, suggesting that the restitution phenomenon is load sensitive.
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