Systolic time intervals during submaximal and maximal exercise in man

This study describes the serial responses of the systolic time intervals (STI) to submaximal and maximal supine exercise in normal subjects. Regression equations relating STI and heart rate during supine submaximal and maximal exercise are derived. It is shown that within the heart rate range of 120 to 170 beats per minute, total electromechanical systole (QS₂) and left ventricular ejection time (LVET) are related inversely and linearly to heart rate for both levels of exercise. At comparable heart rates, the QS₂ and LVET are greater during maximal than submaximal exercise, with differences widening significantly with increasing heart rate. This finding points out the importance of taking into account the intensity of exercise when evaluating STI responses to exercise stress in different groups.The pre-ejection period (PEP) significantly decreases from rest to the initial phase of both maximal and submaximal exercise with a subsequent tendency to plateau, indicating that a minimum PEP is reached early during exercise and that cardiovascular adaptation no longer includes additional shortening.This study also shows that STI obtained during exercise cannot be corrected for heart rate according to regression equations which were developed in resting supine subjects. Thus, there appears to be no justification for extrapolating the heart rate range of resting supine subjects to the exercise state for correcting intervals in this manner. In addition, STI measurements made during the immediate recovery period following supine exercise are significantly different from those obtained just prior to cessation of exercise. Therefore, recovery STI do not reflect the true hemodynamic changes occurring during the course of exercise.The application of the levels of exercise described in this study to the assessment of changes in STI in patients with documented or suspected cardiac dysfunction appears warranted. Alterations in left ventricular performance not evident at rest or following mild exercise might be detected employing these more strenuous exercise protocols. Using the regression equations established in this study, exercise-induced deviation in STI corrected for heart rate may now be determined with the realization that these relationships were derived from relatively young men. However, in the adult population the duration of LVET corrected for heart rate varies little with advancing age, and PEP shows only a slight increase.^34,35     

Prognostic implications of rest and exercise radionuclide ventriculography in patients with suspected or proven coronary heart disease

Rest and exercise radionuclide ventriculography were assessed for their value in predicting major cardiac events in patients with chest pain. Of 219 patients who were followed for up to 51 months, 42 had major cardiac events: 12 patients (5.5%) died, 5 (2.2%) sustained nonfatal myocardial infarction, and 25 (11.4%) had coronary arterial bypass grafting. Univariate and multivariate survival analysis revealed that exercise left ventricular ejection fraction was the best predictor for total major events and the resting ejection fraction to be the best predictor for death or nonfatal myocardial infarction. These two variables were strong predictors in the entire group of patients and in subgroups: patients with or without Q-wave infarction, patients with high probability of coronary artery disease and those with abnormal resting left ventricular function. Thus, radionuclide angiography provides important prognostic data that permits the physician to categorize patients with chest pain syndromes with respect to subsequent cardiac events. If validated, this model or a modification of it could identify patients at high risk of subsequent major cardiac events who are candidates for intensive follow up and therapy or further invasive evaluation, as well as patients at low risk of subsequent major cardiac events for whom standard follow up would be appropriate.     

Unidirectional complete heart block.

Forty-two patients with complete heart block were subjected to electrophysiological studies wherein apart from localization of the site of the conduction defect, ventricular pacing was done to assess ventriculo-atrial (VA) conduction and concealed ventriculo-nodal (VN) conduction. There was evidence of retrograde conduction in the presence of orthograde CHB in 22 patients (52.4 per cent). Fifteen patients (35.7 per cent) had VA conduction and seven (16.6 per cent) had concealed VN conduction. In patients with supra-Hisian CHB, three of the nine patients had VA conduction while of the 11 patients with intra-Hisian CHB, six had retrograde conduction (four with VA and two with concealed VN conduction). In the infra-Hisian CHB group, of the 22 patients, eight had VA conduction and five had concealed conduction. Incremental ventricular pacing induced VA Wenckebach periods at VPR from 110 to 133/minute with a VA interval of 110 to 130 msec. In view of the induction of Wenckebach VA periods, the recording of retrograde H potentials in some cases, and relatively long VA conduction time, it is surmised that retrograde conduction in the presence of orthograde CHB takes place through the AV conduction system.     

Effects of exercise training on left ventricular mass in patients with ischemic heart disease

To determine whether exercise training results in increased left ventricular mass in patients with ischemic heart disease, we obtained echocardiograms in 14 coronary patients before and after an average of seven months (range 3 to 14 months) of supervised arm and leg exercise. Each echocardiogram was interpreted jointly by two blinded observers, using three different measurement conventions and a semiautomated method of analysis to minimize errors of interpretation. Exercise training led to subjective improvement in all 14 patients, and to an objective increase in functional capacity in 13 of 14 patients, as evidenced by an increase in maximal oxygen consumption estimated from symptom-limited treadmill exercise testing (8.8 ± 2.7 (SD) and 10.7 ± 2.5 METS before and after training, respectively, p < 0.01). However, this functional improvement was not accompanied by any significant change in left ventricular end-diastolic diameter, or posterior wall or interventricular septal thickness. Likewise, left ventricular cross-sectional area (CSA), an index of left ventricular mass which corrects for altered ventricular volume and theoretically reflects directional changes in mass despite nonuniform wall thickness, did not change significantly after training by any measurement convention (CSA = 18.0 ± 6.5 and 17.6 ± 6.5 cm² before and after training, respectively, by American Society of Echocardiography measurements). These data strongly suggest that improved functional capacity after exercise training in patients with ischemic heart disease is not due to exercise-induced left ventricular hypertrophy.     

P wave changes on exercise in patients with isolated mitral stenosis

Patients with mitral stenosis usually showed a marked increase in the P negativity following exercise. The P terminal force in Lead V₁ in 20 cases with isolated mitral stenosis was ?0.090 mm. sec. before exercise, which changed to ?0.177 mm. sec. following the single Master two-step test.Normal adults never showed such changes on exercise. The phenomenon was considered to be due to the posterior rotation of the P wave vector in the horizontal plane, which was induced by the enlargement of the left atrial wall on exercise.     

Noninvasive assessment of left ventricular performance in patients with ischemic heart disease: Ear densitographic study during uninterrupted treadmill exercise

Among 738 consecutive patients with chest pain referred for exercise testing, only 17 men fulfilled strict criteria for this pilot study: (1) achievement of at least 90 percent of age-predicted maximal heart rate or etectrocardtographic criteria for a positive test; (2) subsequent coronary anglography; (3) exclusion of prior heart disease; and (4) absence of medication. Measurements of systolic time intervals obtained with ear densitography during early exercise differentiated 10 patients with coronary artery disease (Group 1) from 17 men (7 patients plus 10 normal volunteers) with normal coronary arteries (Group 2). Despite nearly identical heart rate and blood pressure responses In both groups, men In Group 1 had a significantly greater reduction of preelection period (PEP) at 1 minute and 4 minutes as well as a greater decrease hi PEP/LVET (left ventricular ejection time) ratio. Differences were most significant when expressed as percent change of $\text{PEP}\text{LVET}$ ratio from control value (p <0.001 at both 1 minute and 4 minutes). After 4 minutes, men in Group 1 had no further decrease in $\text{PEP}\text{LVET}$ ratio and in 8 of the 10 men $\text{PEP}\text{LVET}$ ratio then increased to peak exercise. By contrast, $\text{PEP}\text{LVET}$ ratio continued to decrease to peak exercise in men In Group 2. The early floor in $\text{PEP}\text{LVET}$ ratio In Group 1 represents limited functional reserve and the subsequent increase suggests functional deterioration. Thus, densHographic systolic time interval measurements during uninterrupted exercise in unmedlcated subjects appear to improve the sensitivity and specificity of the conventional treadmill test.     

Ebstein's anomaly in association with anomalous nodoventricular conduction. Pre-operative and intra-operative electrophysiological studies.

A 13 year old girl with Ebstein's anomaly was investigated for refractory paroxysmal tachycardias and ventricular pre-excitation. Intracardiac electrophysiological studies demonstrated that ventricular pre-excitation was due to conduction in an anomalous nodo-ventricular pathway. Tachycardia occurred as a result of re-entry within the A-V node with pre-excitation during tachycardia due to conduction in the nodo-ventricular pathway. These tachycardias were controlled initially by medical therapy but because of increasing frequency of attacks, occasionally requiring D.C. conversion, further electrophysiological studies and epicardial mapping were undertaken. The epicardial surface of the right ventricle and right atrium were mapped during tachycardia. The results of the studies confirmed that a direct anomalous atrio-ventricular pathway was not present and that re-entrant tachycardia did not involve an accessory pathway of this type. A rapid atrial pacing system was implanted and paroxysmal tachycardias have been successfully controlled.     

Circulatory improvement after hydralazine or isosorbide dinitrate administration in patients with heart failure: Effect on metabolic responses to submaximal exercise

Hydralazine and isosorbide dinitrate can increase the cardiac output during submaximal exercise in patients with heart failure but whether this increase improves oxygen delivery to underperfused exercising muscle is uncertain. To investigate this question, we measured three systemic markers of skeletal muscle oxygen availability—exercise V?O₂, mixed venous lactate concentration and oxygen debt—during submaximal exercise in 15 patients with heart failure both before and after hydralazine (nine patients) or isosorbide dinitrate (eight patients) administration. Hydralazine increased the cardiac output during exercise from 4.9 ± 1.2 liter/min to 6.5 ± 1.8 liter/min (p < 0.01) but had no effect on exercise V?O₂ (control, 531 ± 135 ml/min; hydralazine, 489 ± 102 ml/min), peak lactate concentration (control, 18.3 ± 4.2 mg/dl; hydralazine, 17.9 ± 3.6 mg/dl) or oxygen debt (control, 474 ± 213 ml; hydralazine, 465 ± 170 ml) (all p > 0.10). Isosorbide dinitrate increased the cardiac output during exercise from 4.6 ± 0.9 liter/min to 5.3 ± 0.8 liter/min (p < 0.01) but also did not change exercise V?O₂ (control, 488 ± 62 ml/min; isosorbide, 473 ± 44 ml/min), peak lactate concentration (control, 19.2 ± 6.0 mg/dl; isosorbide, 21.4 ± 8.2 mg/dl) or oxygen debt (control, 522 ± 154 ml; isosorbide, 445 ± 147 ml) (all p > 0.10). We conclude that short-term administration of hydralazine or nitrates to patients with heart failure can substantially improve circulatory function during exercise but that this improvement probably does not enhance skeletal muscle nutritional flow.     

Is the treadmill exercise test useful for evaluating coronary artery disease in patients with complete left bundle branch block?

To aid in the study of coronary artery disease, 57 patients with complete left bundle branch block underwent clinical evaluation, treadmill exercise testing and cardiac catheterization. The patients were classified into two groups according to coronary anglographic findings: 30 patients with significant stenosis (70 percent or greater luminal narrowing) of at least one major vessel and 27 with no significant coronary artery disease. There was no difference in age, presenting symptoms or previous medical treatment between the two groups. There were more men in the group with coronary artery disease. Exercise-induced S-T changes were similar in the two groups; the sensitivity and specificity of these changes for the diagnosis of coronary artery disease were unacceptable irrespective of the criterion chosen. With additional S-T depression of either 1 or 2 mm below the baseline value, the predictive accuracy was only 53 percent. Combined exertional chest pain and 1 mm S-T depression increased the predictive accuracy of exercise testing to 71 percent. These data indicate that exercise-induced electrocardiographic changes do not facilitate detection of coronary artery disease in patients with complete left bundle branch block.     

Left ventricular performance during exercise in patients with left bundle branch block: evaluation by gated radionuclide ventriculography

To investigate changes in left ventricular (LV) function during exercise in patients with left bundle branch block (LBBB), 22 patients without a history or physical findings of previous myocardial infarction or LV dysfunction were studied by gated radionuclide ventriculography (GRNV) at rest and during bicycle exercise. Coronary arteriography demonstrated greater than 75% diameter narrowing of at least one coronary artery in nine patients. Of the remaining 13 patients, GRNV demonstrated wall motion abnormalities in seven patients either at rest or with exercise. During exercise, mean ejection fraction (EF) did not increase in patients without coronary artery disease (CAD). Patients with CAD had a 12-point fall in mean EF with exercise. We conclude that LV reserve, as demonstrated by ability to increase EF with exercise, is impaired in patients with LBBB even in the absence of CAD or other underlying cardiac disease and that standard GRNV criteria to exclude the presence of CAD (a greater than five-point increase in EF with exercise and normal wall motion) are not strictly applicable in screening patients with LBBB.     

The effect of dobutamine on exercise performance in patients with symptomatic ischemic heart disease

The effect of dobutamine on exercise performance was assessed in 20 patients with ischemic heart disease (CAD) and a positive stress test. These patients had a wide range of resting left ventricular ejection fraction (range 22% to 69%, mean 42%). Each patient entered a double-blind crossover study in which two identical exercise radionuclide ventriculograms were performed in patients on dobutamine, 5 micrograms/kg/min intravenously, or placebo. Dobutamine increased resting left ventricular ejection fraction. Although ejection fraction fell with dobutamine during submaximal exercise, it remained higher than with placebo. At peak exercise, ejection fraction fell to the same level on dobutamine as with placebo. Dobutamine diminished exercise time and time to ischemia while peak pressure-rate product was unchanged. Four of 20 patients developed complex ventricular premature beats, all while on dobutamine. Although useful when administered to resting patients with acute left ventricular failure, dobutamine's effects may be deleterious in exercising patients with chronic ischemic heart disease.     

Primary risk factors in patients with myocardial infarction.

A predicted probability of suffering myocardial infarction based on a multiple risk function involving serum cholesterol, systolic blood pressure, and tobacco consumption, was allocated retrospectively to 270 men who survived a primary myocardial infarction. The infarction patients were representative of all surviving, diagnosed cases of primary infarction in men in certain age groups in G?teborg, Sweden, during the years 1968-70. The patients were divided into three groups-low, moderate, and high risk. A large number of patients had suffered infarction despite relatively low risk, but the patients showed a tendency toward higher risk in comparison with the risk distribution in a representative population sample. In order to study whether other variables, not included in the risk function, could "explain" the infarction in patients with relatiely low risk, the different risk groups were compared. A high degree of mental stress, diabetes mellitus, and dyspnea on exertion, and possibly also raised triglycerides, contributed to "explain" the infarctions in the low-risk group. Low physical activity during leisure time was probably also of importance.     

Maximal exercise in children with aortic regurgitation: an adjunct to noninvasive assessment of disease severity

Twenty-five asymptomatic children with chronic aortic regurgitation were evaluated by graded bicycle exercise testing and standard resting M-mode echocardiogram. These results were compared to those of 35 normal controls matched for age and body surface area. Twenty-one patients underwent cardiac catheterization to rule out associated lesions. Patients fell into two groups based upon the left ventricular end-diastolic volume per body surface area (LVEDVI): group I (n = 10) had LVEDVI less than or equal to 2 SD from the mean of normal; group II (n = 15) had LVEDVI greater than or equal to 4 SD from the mean of normal. All had normal shortening fraction and velocity of circumferential fiber shortening. At maximal exercise, patients in group I were found to have no significant differences from normals in maximal workload, total work, percent maximal oxygen consumption, heart rate, blood pressure, or ST segment depression. However, patients in group II had blunted mean maximal exercise heart rate (p less than 0.001), systolic hypertension (p less than 0.05), and increased frequency and maximal amplitude of ST depression (p less than 0.01, p less than 0.001, respectively) compared to normal controls. Within group II the mean maximal amplitude of ST depression was significantly related to increasing LVEDVI (r = 0.53, p less than 0.05). The mean maximal exercise heart rate, systolic blood pressure, and maximal amplitude of ST segment depression were significantly related to LVEDVI for patient groups and normal controls together (r = -0.384, p less than 0.01; r = 0.28, p less than 0.05; r = 0.70, p less than 0.001, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Response to isometric exercise in children and young adults with aortic regurgitation

We studied the hemodynamic response to isometric exercise in 28 children and young adults with aortic regurgitation (AR). Results were compared with those of 18 control subjects without heart disease. Sustained isometric exercise at 33% maximal handgrip capability produced similar increase in heart rate in the two groups. Systolic blood pressure rose to a greater extent in patients with AR than in controls (mean rise 33 mm Hg vs 13 mm Hg). Thirteen of 28 patients with AR had elevated left ventricular end-diastolic diameters at rest. During isometric exercise, left ventricular end-diastolic diameter remained constant in both groups. However, end-systolic diameter increased in patients with AR, resulting in a fall in shortening fraction. The mean left ventricular shortening traction of the patients with AR fell from 36.0 ± 1.0% to 32.8 ± 1.2% (p < 0.001), but did not change in controls. The fall in shortening fraction was most marked in patients with severe AR. We conclude that patients with AR have an abnormal cardiovascular response to isometric exerclse consisting of greater increase in blood pressure and a decrease in left ventricular fractional shortening.     

Quantification of the Frank and McFee-Parungao orthogonal electrocardiogram in valvular pulmonic stenosis. Correlations with hemodynamic measurement.

In 66 patients with congenital valvular pulmonic stenosis and intact ventricular septum, correlations were obtined among various multiple hemodynamic and orthogonal vectorcardiographic parameters. The Frank and McFee-parungao lead systems were used. The most important hemodynamic parameter evaluated was right ventricular pressure (RVP). RVP correlated best with X terminal to the right (XTR) in both Frank (R = 0.68) and McFee (R = 0.61) systems. The correlation between RVP and Z anterior was poor. The direction of the initial QRS vector on the X axis was helpful in predicting severity. With X initial to the right, especially in McFee, the RVP is most likely to be systemic or less, while with X initial to the left, the RVP is frequently but not necessarily suprasystemic. T vector spatial orientation is not helpful in the assessment of severity.     

Ascending aorta-pulmonary artery anastomosis for cyanotic congenital heart disease.

The course and prognosis of 208 patients with an ascending aorta to pulmonary artery anastomosis is reviewed. Mortality rate during, or within one month, of surgery was 24 per cent (50/208) and late mortality rate, prior to repair, was 10 per cent (21/208). An additional 5 per cent (10/208) died during subsequent intracardiac repair. Congestive heart failure developed in 25 per cent (53/208), pulmonary artery hypertension in 17 per cent (12/72), and pulmonary vascular obstruction in 6 per cent (4/72). An increase in orifice size of the stoma with time was documented in eight patients. Additional subsequent palliative surgery was required in 22 per cent (45/208). Mortality rate was directly related to age at operation and was highest in neonates less than one week of age. In infants with tetralogy of Fallot, a preliminary comparison of mortality rate between palliative surgery and primary repair clearly suggests that the latter is the preferred method of treatment.