Cardiac response to exercise in patients with chronic aortic regurgitation

Aortic Regurgitation and Heart Failure: Advances in Diagnosis, Management, and Interventions

This review discusses the contemporary clinical evaluation and management of patients with comorbid aortic regurgitation (AR) and heart failure (HF) (AR-HF). Importantly, as clinical HF exists along the spectrum of AR severity, the present review also details novel strategies to detect early signs of HF before the clinical syndrome ensues. Indeed, there may be a vulnerable cohort of AR patients who benefit from early detection and management of HF. Additionally, while the mainstay of operative management for AR has historically been surgical aortic valve replacement, this review discusses alternate procedures that may be beneficial in high-risk cohorts.

Mathematical analysis of the effects of valvular regurgitation on the pumping efficacy of continuous and pulsatile left ventricular assist devices

•

We numerically investigated the physiological relationship between the severity of regurgitation and the effect of a left ventricular assist device (LVAD) on cardiovascular system responses.

•

Under conditions of mitral regurgitation, the effects of both pulsatile and continuous LVAD treatment on ventricular unloading were significant.

•

Under conditions of aortic regurgitation (AR), the effects of the LVADs on ventricular unloading were not significant. The effects of LVAD treatment decreased according to the severity of AR.

Background

A left ventricular assist device (LVAD) is normally contraindicated in significant aortic regurgitation (AR) and requires intraoperative valve repair or exclusion. Nevertheless, AR can coexist with an LVAD, so a valid question when asked might still be of clinical significance. The purpose of this study is to analyze the effects of valve regurgitation on the pumping efficacy of continuous and pulsatile LVADs with a computational method.

Methods

A cardiovascular model was developed based on the Windkessel model, which reflects the hemodynamic flow resistance and the blood wall elasticity. Using the Windkessel model, important cardiovascular components, such as the right atrium, right ventricle, pulmonary artery, pulmonary vein, left atrium (LA), left ventricle (LV), aorta, and branching blood vessels, were expressed.

Results

In the case of AR, continuous and pulsatile LVADs improved cardiac output and reduced mechanical load slightly. In the case of mitral regurgitation, the LVADs improved cardiac output (cardiac outputs were about 5 L/min regardless of the severity of regurgitation) and reduced afterload significantly.

Conclusion

AR reduced both continuous and pulsatile LVAD function significantly while mitral regurgitation did not affect their pumping efficacy.

Maximal oxygen uptake in severe aortic regurgitation: a different view of left ventricular function

Respiratory gas exchange was used to assess left ventricular (LV) function in 22 patients with severe aortic regurgitation (19 men and three women, aged 18 and 70 years, mean 49 years). Anaerobic threshold and symptom-limited maximal oxygen consumption (VO2 max) were measured during treadmill exercise, and the results were compared with conventional echocardiographic and radionuclide indices of LV systolic function. The results were considered with respect to the patients' New York Heart Association functional class. Both rest and exercise LV ejection fractions were variable, but the mean results were similar in all classes. The echocardiographic indices of LV cavity dimensions, fractional shortening, radius/thickness ratio, and systolic wall stress also showed a wide range but with similar mean results in each class. In contrast, VO2 max and anaerobic threshold showed a relationship to functional class. VO2 max was 32.4 +/- 3.4 ml/kg/min in age-matched control subjects; in the patients it was 27.9 +/- 4.7 in class I, 24.7 +/- 5.7 in class II, and 14.2 +/- 2 in the combined class III/IV. Results in patients in classes I and II were similar, but both groups were significantly different from control subjects (p less than 0.05) and from patients in class III/IV (p less than 0.01). About half of the patients with moderate LV dysfunction (judged by reduced VO2 max) were asymptomatic, and LV function was impaired in 4 of 10 patients in class I. Thus, unlike conventional indices of LV function, VO2 max appeared capable of distinguishing patients with moderate-to-severe LV dysfunction from those with little or no LV dysfunction. Measurement of respiratory gas exchange appears to be a valid and useful supplementary means of assessing LV function in severe aortic regurgitation. Further long-term evaluation is required.

Effects of exercise on left ventricular volume and output changes in severe mitral regurgitation. A radionuclide angiographic study

Symptom-limited supine bicycle exercise with radionuclide angiography was performed on 11 patients with severe mitral regurgitation (who were not receiving vasodilators), to assess changes in left ventricular volume, regurgitant fraction, forward flow and regurgitant flow during exercise. All patients were in normal sinus rhythm with a normal resting ejection fraction (greater than 0.50). During exercise, the end-diastolic volume index, end-systolic volume index, ejection fraction, and regurgitant fraction of the left ventricle did not change significantly. The forward cardiac index increased by 86 percent (p less than 0.01) with exercise. This increase was explained by an 87 percent increase in the heart rate (p less than 0.01); there was no significant change in the forward stroke volume index. Although the regurgitant stroke volume index declined by 12 percent with exercise (p = 0.07), the regurgitant flow increased markedly by 64 percent (p less than 0.01) to a mean of 8.2 L/min/m2. These data indicate that in patients with severe mitral regurgitation, the increase in the exercise forward flow is totally dependent on the heart rate response. There is a marked increase in regurgitant flow during exercise, which presumably contributes to dyspnea.

Effect of digoxin and vasodilators on left ventricular function in aortic regurgitation

In order to assess the relative value of digoxin, nifedipine and hydralazine on left ventricular performance at rest and during exercise, we studied 10 men with moderately severe chronic aortic regurgitation using two-dimensional echocardiography. Digoxin after one month at therapeutic serum levels increased resting ejection fraction as compared to control [0.54 +/- 0.08 (SD) vs 0.47 +/- 0.08, respectively, P less than 0.03]. Ejection fraction decreased during exercise but the difference between digoxin and control was maintained. Stroke volume also was higher on digoxin than control at rest (93 +/- 15 vs 83 +/- 17 ml, P less than 0.02) and the larger stroke volume on digoxin was maintained during exercise. By contrast, stroke volume was reduced by one month of therapy with maximally tolerated nifedipine doses compared to control (74 +/- 8 vs 83 +/- 17 ml, P = 0.03) and this difference was maintained during exercise. Hydralazine in doses up to 225 mg/day for one month produced no significant changes in left ventricular performance compared to control at rest or during exercise. However, compared to digoxin ejection fraction at peak exercise was significantly less on hydralazine (0.39 +/- 0.9 vs 0.52 +/- 10, P less than 0.02). These data suggest that digoxin improved left ventricular performance and may be of benefit in the treatment of patients with chronic aortic regurgitation.

Factors influencing the variations of ejection fraction during exercise in chronic aortic regurgitation

The influence of left ventricular volume variations and regurgitant fraction variations upon left ventricular ejection fraction during exercise was examined using equilibrium radionuclide angiography in patients suffering from aortic regurgitation. Ejection fraction (EF), regurgitant fraction (RF), end diastolic volume (EDV) and end systolic volume (ESV) variations from rest to peak exercise were determined in 44 patients suffering from chronic aortic regurgitation (AR) and in 8 healthy volunteers (C). In C, EF increased (+0.10 +/- 0.03, P less than 0.01) and ESV decreased significantly (-23% +/- 12%, P less than 0.01), RF and EDV did not vary significantly. In AR patients, EF, EDV and ESV did not vary significantly because of important scattering of individual values. Changes in EF and ESV were inversely correlated (r = -0.79, P less than 0.01) and RF decreased significantly (-0.12 +/- 0.10, P less than 0.01). Volumes and EF changes during exercise occurred in three different ways. In a 1st subgroup of 7 patients, EF increased (+0.09 +/- 0.03, P less than 0.05) in conjunction with a reduction of ESV (-24% +/- 12%, P less than 0.05) without a significant change in EDV. In a 2nd group of 22 patients, EF decreased (-0.04 +/- 0.07, P less than 0.01) in association with an increase in ESV (+17% +/- 16%, P less than 0.01) and no change in EDV. In a 2nd group of 22 patients, EF decreased (-0.04 +/- 0.07, P less than 0.01) in association with an increase in ESV (+17% +/- 16%, P less than 0.01) and no change in EDV. In a 3rd subgroup of 15 patients, EF decreased (-0.02 +/- 0.06, P less than 0.01) despite a reduction in ESV (-7% +/- 6%, P less than 0.01) because of a dramatic EDV decrease (-10% +/- 6%, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic implications of left ventricular function during exercise in asymptomatic patients with aortic regurgitation

Few data are available that address the prognostic implications of the response of the left ventricle (LV) to exercise in asymptomatic patients with aortic regurgitation (AR) who have normal resting LV function. Thirty-one such patients were contacted two to seven years after rest and exercise radionuclide ventriculography. Eleven had had significant cardiovascular events. Event-free survival at forty-eight months was 64%. Ten of eleven events occurred in 21 patients with decline in ejection fraction (EF), but the magnitude of decline did not further separate the group with regard to prognosis. Eight events (73% of total events) occurred in the 11 patients (35% of total patients) with an EF during exercise of 0.55 or less. The short and intermediate outlook for asymptomatic patients with AR and normal resting LV function is good regardless of the response of the EF to exercise, but an exercise EF less than or equal to 0.55 does identify a relatively high-risk subset for deterioration beyond twenty-four months.

Radionuclide angiographic evaluation of left ventricular performance at rest and during exercise in patients with aortic regurgitation

Radionuclide angiographic evaluation of LV performance at rest and during exercise in patients with AR have shown that an abnormal EF response to exercise may be observed in asymptomatic patients with normal resting LV function. The EF response to exercise has been correlated with a number of clinical and exercise measurements; important among these are the slope of the systolic pressure-to-end-systolic volume, end-systolic volume, cardiac index, pulmonary capillary wedge pressure, and wall stress. The changes in the regurgitant fraction, EF, and LV volume have shown considerable individual variability; they have also allowed a better understanding of the circulatory responses during exercise. Radionuclide angiography provides a reliable and reproducible method of measuring the rest LVEF that is important in the timing and the outcome of valve replacement. The value of the EF response to exercise in patient management is not yet clear; it is possible that other radionuclide-derived measurements at rest or during exercise, such as the systolic pressure-to-end-systolic volume relationship, and the end-systolic volume may provide complementary information to that provided by the EF.

Left ventricular pressure/volume relationship in aortic regurgitation

In this study we examined the left ventricular pressure/volume relationship in 39 patients with moderate or severe aortic regurgitation (AR) and 15 normal subjects. The patients with AR were divided into two groups; patients with normal resting ejection fraction (EF greater than or equal to 50%, group I, n = 21) and patients with abnormal EF (group II, n = 18). The patients in group I were younger (p less than 0.005), exercised to a higher workload, and had better exercise tolerance than patients in group II (p less than 0.01). The patients' exercise heart rate and blood pressure were not significantly different between the two groups. During exercise tests nine patients in group I and seven patients in group II had normal EF response (greater than or equal to 5% increase) (p = NS). The peak systolic blood pressure to end-systolic volume index ratio (SBP/ESVI) was higher in normal subjects than in patients in groups I and II, at rest it was (4.3 +/- 1.0 vs 2.6 +/- 1.2 vs 1.6 +/- 0.8, respectively, p less than 0.0001) and during exercise it was (7.6 +/- 1.8 vs 4.2 +/- 1.4 vs 2.6 +/- 1.3, respectively, p less than 0.0001). The resting SBP/ESVI ratio was below the lower normal limit in 12 patients (57%) in group I and in 16 patients (89%) in group II. Also, the exercise SBP/ESVI ratio was below the lower normal limit in 17 patients (81%) in group I and all of the patients (100%) in group II. Multivariate discriminant analysis identified the change in SBP/ESVI (F = 34.8) and resting end-diastolic volume (F = 6.7) as independent predictors of the EF response to exercise. Thus, most patients with AR, including those with normal resting EF or normal EF response to exercise, have abnormal SBP/ESVI at rest or during exercise.

Rest-exercise radionuclide angiographic assessment of left ventricular function in chronic aortic regurgitation: significance of serial studies in medically versus surgically treated groups

Forty consecutive asymptomatic patients with chronic aortic regurgitation who underwent three serial yearly rest and postexercise radionuclide angiograms were compared with 27 consecutive patients with chronic aortic regurgitation and aortic valve replacement who were studied preoperatively, 3 and 15 months postoperatively. Patients were divided into four subgroups based upon the resting left ventricular ejection fraction and the functional reserve on the initial study. Of the 40 medically treated patients, 19 (47.5%) and 24 (60%) demonstrated a response at least one type lower at 12 months and 24 months, respectively. Initial functional reserve, initial duration of exercise, and the change in exercise duration during the 24 months was not associated with changes in resting or postexercise left ventricular ejection fraction. A seesaw pattern was observed between the resting and the postexercise left ventricular ejection fraction as ventricular function deteriorated. We observed in the surgical groups a reversal of the seesaw interaction between the resting and postexercise ejection fraction seen in the medical patients. In the surgical groups the left ventricular end-diastolic pressure, initial functional reserve, initial duration of exercise, and change in exercise duration postoperatively were not predictors of improvement in left ventricular function at 15 months. Comparing medical and surgical serial data, we suggest yearly radionuclide angiographic determination of rest left ventricular ejection fraction in asymptomatic patients with chronic aortic regurgitation. When the rest ejection fraction is less than 50%, exercise angiography should be performed to determine functional reserve. When functional reserve is also abnormal, surgery should be recommended.

Comparison of effects of isometric and supine bicycle exercise on left ventricular performance in patients with aortic regurgitation and normal ejection fraction at rest

The effects of handgrip and supine bicycle exercise on hemodynamics and left ventricular (LV) performance were compared in 25 patients with moderate to severe aortic regurgitation (AR) and normal LV ejection fraction at rest (greater than or equal to 50%) and in 10 control subjects. In both groups, heart rate, systolic blood pressure, rate-pressure product, and LV output were higher during supine bicycle exercise. Compared with the controls, in patients with AR, stroke volume was unchanged during supine bicycle exercise. LV end-diastolic volume increased during handgrip exercise but was unchanged during supine bicycle exercise. LV end-systolic volume increased and ejection fraction decreased during both forms of exercise. Of 25 patients with AR, 15 (60%) during handgrip exercise and 19 (76%) during supine bicycle exercise had an abnormal ejection fraction response (p less than 0.05). In patients with moderate to severe AR and normal LV ejection fraction at rest, both handgrip and supine bicycle exercise induced LV dysfunction. An abnormal LV ejection fraction response occurred more often with supine bicycle exercise. Handgrip exercise may be a useful alternative method for detecting LV dysfunction in patients with AR in whom adequate bicycle exercise cannot be accomplished.

Association between the exercise ejection fraction response and systolic wall stress in patients with chronic aortic insufficiency

We studied the exercise ejection fraction response in 56 patients with chronic aortic insufficiency. All had left ventricular dilatation but preserved resting ejection fraction and minimal or no symptoms. The exercise ejection fraction increased by 0.05 units or greater in 18 (32%) patients (group I), remained within 0.05 units of the resting value in 18 (32%) patients (group II), and fell by 0.05 units or greater in 20 (36%) patients (group III). There were no significant differences among the groups in left ventricular end-diastolic dimension, end-systolic dimension, or fractional shortening by echocardiography or in resting left ventricular volumes and ejection fraction by radionuclide angiography. Left ventricular end-systolic wall stress was significantly higher in group III than in either group I or group II (89 +/- 20 vs 70 +/- 18 and 69 +/- 17 X 10(3) dyne/cm2; p less than .005). At peak exercise there were no differences among groups in systolic blood pressure. However, end-systolic volume increased from 65 +/- 28 to 77 +/- 36 ml/m2 in group III and fell from 50 +/- 21 to 28 +/- 18 ml/m2 in group I during exercise. Thus, at peak exercise end-systolic volume was nearly three times greater in group III than in group I. Although stress could not be determined directly during exercise, the directional changes in its determinants suggest that it also would have been higher in group III patients. A highly significant inverse correlation was present between the ejection fraction response and the change in end-systolic volume (r = -.87, p less than .0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of upright and supine position on cardiac rest and exercise response in aortic regurgitation

The effects of upright and supine position on cardiac response to exercise were assessed by radionuclide ventriculography in 15 patients with moderate to severe aortic regurgitation (AR) and in 10 control subjects. In patients with AR, heart rate was higher during upright exercise, but systolic and diastolic blood pressure and left ventricular (LV) output were similar during both forms of exercise. LV stroke volume and end-diastolic volume were not altered during supine exercise. LV end-systolic volume increased and ejection fraction decreased during supine exercise, but both were unchanged during upright exercise. Of 15 patients, 5 in the upright and 12 in the supine position had an abnormal LV ejection fraction response to exercise (p less than 0.01). Right ventricular ejection fraction increased and regurgitant index decreased with both forms of exercise and was not significantly different between the 2 positions. Thus, posture is important in determining LV response to exercise in patients with moderate to severe AR.

Evaluation of relationship between myocardial contractile state and left ventricular function in patients with aortic regurgitation

We studied the relationship between myocardial contractile state and left ventricular functional response to exercise in 14 asymptomatic patients with isolated moderate-to-severe aortic regurgitation and six control subjects. The slope of the systolic blood pressure-left ventricular end-systolic volume (pressure-volume) relationship determined by radionuclide ventriculography during angiotensin infusion was used as an indirect measure of myocardial contractility and was compared with left ventricular ejection fraction at rest and during both isometric handgrip and dynamic bicycle exercise. The slope of the pressure-volume relationship was significantly lower in patients with aortic regurgitation than in the control subjects (1.75 +/- 0.57 vs 2.78 +/- 0.42, p less than 0.01). The slope correlated exponentially with resting ejection fraction and was linearly related to changes in left ventricular ejection fraction during both handgrip and bicycle exercise. In patients with aortic regurgitation, resting ejection fraction may overestimate myocardial function. The slope of the pressure-volume relationship measured during afterload stress and left ventricular ejection fraction response to exercise intervention more reliably reflect the degree of left ventricular dysfunction.

Noninvasive assessment of acute effects of nifedipine on rest and exercise hemodynamics and cardiac function in patients with aortic regurgitation

The acute effects of nifedipine (20 mg sublingually) on hemodynamics and cardiac function were studied at rest and during supine bicycle exercise in 20 patients with aortic regurgitation. At rest, heart rate increased by 13%, systemic vascular resistance decreased by 34% and regurgitant index decreased by 17%. The change in systemic vascular resistance was related to its initial rest level (r = 0.82, p less than 0.001) and to the changes in forward cardiac output (r = 0.58, p less than 0.01) and regurgitant index (r = 0.60, p less than 0.01). Left ventricular end-diastolic and end-systolic volumes, stroke volume and ejection fraction were unchanged, whereas right ventricular ejection fraction increased. During exercise, nifedipine administration further increased heart rate by 8% and decreased systemic vascular resistance by 19%. Both forward stroke volume and forward cardiac output increased, but total left ventricular stroke volume was unchanged, resulting in a significant decrease in regurgitant index. Although left ventricular end-diastolic volume was slightly decreased, end-systolic volume did not increase; thus, ejection fraction was higher than that during control exercise (p less than 0.01). Right ventricular ejection fraction increased further. In aortic regurgitation, the acute administration of nifedipine improved cardiac performance and reduced regurgitation at rest and during exercise as a result of afterload reduction and increased heart rate. Whether these beneficial effects will occur during long-term therapy requires further investigation.

Echocardiographic evaluation of the response to afterload stress test in young asymptomatic patients with chronic severe aortic regurgitation: sensitivity of the left ventricular end-systolic pressure-volume relationship

The detection of myocardial depression is an important goal in the management of patients with chronic severe aortic regurgitation but may be quite difficult at an early stage by the conventional basal measures of contractility. The response to afterload stress determined by angiotensin challenge and the end-systolic pressure-volume relationship was evaluated echocardiographically in 16 asymptomatic or mildly symptomatic patients with chronic severe aortic regurgitation, ages 15 to 56 years (mean 32 +/- 12). Nine normal subjects, ages 25 to 41 years (mean 31 +/- 5), served as a control group. In the group with aortic regurgitation, end-systolic dimensions were greater than 55 mm in five of 16 patients and fractional shortening was 25% or less in two of 16. In the control group angiotensin caused a decrease of stroke volume index in six out of nine patients (15% at the most) and a mild increase in three. In the group with aortic regurgitation stroke volume index decreased by 15% or more of the basal value in nine of 16 patients and increased or decreased by less than 15% in seven of 16. Ejection fraction decreased in both groups, from 61 +/- 6% to 52 +/- 7% in the control group and from 56 +/- 6% to 45 +/- 5% in the group with aortic regurgitation. Ventricular function curves were derived by relating end-diastolic volume index to stroke work index; seven of 16 patients had abnormal responses reflecting an afterload mismatch.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormal left ventricular response to isometric exercise in pure, isolated aortic regurgitation: beneficial effects of nifedipine

To examine the effects of nifedipine on the left ventricular (LV) functional response to isometric exercise in patients with aortic regurgitation (AR), 20 patients with isolated, moderate to severe AR performed 3 minutes of handgrip exercise at 33% of their maximal voluntary contraction, before and after administration of 20 mg of sublingual nifedipine. Although handgrip exercise produced similar increases in heart rate and systolic blood pressure before and after nifedipine treatment, heart rate was higher and systolic blood pressure lower with handgrip exercise during nifedipine treatment. LV end-diastolic volume index was not different during the control period and nifedipine handgrip exercise, but the increase in end-systolic volume index was smaller and the ejection fraction was higher during nifedipine handgrip exercise. Nifedipine reduces afterload and ameliorates handgrip exercise-induced LV dysfunction in patients with AR.

Mechanism and significance of a decrease in ejection fraction during exercise in patients with coronary artery disease and left ventricular dysfunction at rest

The purpose of this study was to determine whether an exercise-induced decrease in ejection fraction in patients with coronary artery disease and left ventricular dysfunction at rest represents ischemia or the nonspecific response of a compromised left ventricle to exercise stress. Accordingly, radionuclide ejection fraction responses of 246 patients with coronary artery disease and an ejection fraction at rest of less than 0.50 were compared with those of a "nonischemic" control group of 48 patients with idiopathic dilated cardiomyopathy and a similar degree of ventricular dysfunction. The significance of the ejection fraction response in the group with coronary artery disease was further examined by relating it to the angiographic extent of coronary artery disease, severity of angina, incidence of chest pain and electrocardiographic ST segment depression during exercise and long-term prognosis. The ejection fraction decreased by greater than or equal to 0.01 and greater than or equal to 0.05 during exercise in 48 and 28%, respectively, of the patients with coronary artery disease compared with only 8 and 2%, respectively, of the patients with cardiomyopathy. When exercise was limited by fatigue at a submaximal heart rate, the ejection fraction decreased in 25% of the patients with coronary artery disease but in none of the patients with cardiomyopathy. Patients with coronary artery disease whose ejection fraction decreased during exercise had a significantly higher incidence of three vessel disease, exercise-induced chest pain or ST depression and late mortality than did patients whose ejection fraction did not decrease. These relations were confirmed equally in subgroups of patients with moderate (ejection fraction 0.30 to 0.49) and severe (ejection fraction less than 0.30) left ventricular dysfunction. Thus, in patients with coronary artery disease and left ventricular dysfunction at rest, a decrease in ejection fraction during exercise is more likely to indicate ischemia than a nonspecific left ventricular response to exercise stress. In the individual patient, a decrease of 0.05 or greater, or a decrease during submaximal exercise, appears to be highly specific for ischemia. A decrease in ejection fraction identifies a subgroup of patients with a high prevalence of multivessel coronary artery disease and a high risk of death during long-term follow-up on medical therapy.

Regulation of cardiac output during upright exercise in patients with aortic regurgitation

The change in cardiac output during upright exercise in patients with aortic regurgitation (AR) is not well known. We measured left ventricular (LV) ejection fraction (EF) and volume, regurgitant fraction (RF), total cardiac output and forward cardiac output at rest, and peak upright exercise by means of radionuclide angiography in ten normal subjects and 15 patients with AR. In the normal subjects, there was no significant change in the end-diastolic volume but there was a significant decrease in the end-systolic volume (p = 0.0001) and a significant increase in EF (p = 0.0001). The increase in cardiac output during exercise was due to increases in both stroke volume and heart rate. In patients with AR, there was a significant decrease during exercise in RF (53 +/- 15% at rest, and 45 +/- 15% during exercise; p = 0.03), and in end-diastolic and end-systolic volume (p = 0.02, and p = 0.003, respectively). The EF increased during exercise (p = 0.003). The total stroke volume did not change (68 +/- 19 ml/m2 at rest, and 67 +/- 14 ml/m2 during exercise; p, NS). Thus, in patients with AR, individual changes in EF, RF, and volume are quite variable, but as a group a decrease in RF and an increase in heart rate contribute to the increase in forward flow. The total stroke volume may not increase during exercise, despite an increase in EF and a decrease in end-systolic volume because of a concomitant decrease in end-diastolic volume.

Blood pressure in black, white and Asian factory workers in Birmingham

A screening survey was conducted among factory workers, aged 15-64 years, in Birmingham, England to investigate ethnic differences in blood pressure. One-thousand and forty-nine subjects (784 men, 265 women) were screened, representing 79% of the eligible population. Mean systolic and diastolic blood pressures generally did not differ between men of black West Indian (n = 173), local white (n = 439) or Asian (n = 172) origin, when matched by 10-year age groups. Analysis of covariance using age as the covariate revealed that, overall, Asian men had significantly lower systolic but higher diastolic pressures than the other ethnic groups. The proportion of men arbitrarily defined as hypertensive (greater than or equal to 160 mmHg systolic or greater than or equal to 95 diastolic or blood pressures below this figure whilst receiving antihypertensive therapy) was 26% of West Indians, 22% of whites and 17% of Asians, but these were not significantly different when age was accounted for. Black West Indian women (n = 101) did have higher diastolic pressure than white women (n = 164), but this difference was dependent on body mass index. Overall, systolic pressures in women were not significantly different. These findings differ from those consistently reported from the United States.

Left ventricular function in chronic aortic regurgitation

Left ventricular performance was determined in 42 patients with moderate or severe aortic regurgitation during upright exercise by measuring left ventricular ejection fraction and volume with radionuclide ventriculography. Classification of the patients according to exercise tolerance showed that patients with normal exercise tolerance (greater than or equal to 7.0 minutes) had a significantly higher ejection fraction at rest (probability [p] = 0.02) and during exercise (p = 0.0002), higher cardiac index at exercise (p = 0.0008) and lower exercise end-systolic volume (p = 0.01) than did patients with limited exercise tolerance. Similar significant differences were noted in younger patients compared with older patients in ejection fraction at rest and exercise (both p = 0.001) and cardiac index at rest (p = 0.03) and exercise (p = 0.0005). The end-diastolic volume decreased during exercise in 60% of the patients. The patients with a decrease in volume were significantly younger and had better exercise tolerance and a larger end-diastolic volume at rest than did patients who showed an increase in volume. The mean corrected left ventricular end-diastolic radius/wall thickness ratio was significantly greater in patients with abnormal than in those with normal exercise reserve (mean +/- standard deviation 476 +/- 146 versus 377 +/- 92 mm Hg, p less than 0.05). Thus, in patients with chronic aortic regurgitation: 1) left ventricular systolic function during exercise was related to age, exercise tolerance and corrected left ventricular end-diastolic radius/wall thickness ratio, and 2) the end-diastolic volume decreased during exercise, especially in younger patients and patients with normal exercise tolerance or a large volume at rest.

Exercise testing in asymptomatic or minimally symptomatic aortic regurgitation: relationship of left ventricular ejection fraction to left ventricular filling pressure during exercise

Exercise radionuclide angiography is being used to evaluate left ventricular function in patients with aortic regurgitation. Ejection fraction is the most common variable analyzed. To better understand the rest and exercise ejection fraction in this setting, 20 patients with asymptomatic or minimally symptomatic severe aortic regurgitation were studied. All underwent simultaneous supine exercise radionuclide angiography and pulmonary gas exchange measurement and underwent rest and exercise measurement of pulmonary artery wedge pressure (PAWP) during cardiac catheterization. Eight patients had a peak exercise PAWP less than 15 mm Hg (group 1) and 12 had a peak exercise PAWP greater than or equal to 15 mm Hg (group 2). Group 1 patients were younger and more were in New York Heart Association class I. Group 1 patients also had a higher mean rest ejection fraction (0.64 +/- 0.08 vs 0.49 +/- 0.13, p less than 0.01, higher exercise ejection fraction (0.63 +/- 0.10 vs 0.40 +/- 0.18, p less than 0.01), lower end-systolic volume (38 +/- 13 vs 79 +/- 36 ml/m2, p less than 0.01) and higher peak oxygen uptake (24.9 +/- 5.1 vs 16.6 +/- 4.9 ml/kg/min, p less than 0.01) than group 2 patients. However, the two groups had similar cardiothoracic ratios, changes in ejection fractions with exercise, and rest and exercise regurgitant indexes. Using multiple regression analysis, the best correlate of the exercise PAWP was peak oxygen uptake (r = -0.78, p less than 0.01). No other measurement added significantly to the regression. When peak oxygen uptake was excluded, rest and exercise ejection fraction also correlated significantly (r = -0.62 and r = -0.60, respectively, p less than 0.01). Patients with asymptomatic or minimally symptomatic severe aortic regurgitation have a wide spectrum of cardiac performance in terms of the PAWP during exercise. The absolute rest and exercise ejection fraction and the level of exercise achieved are noninvasive variables that correlate with exercise PAWP in aortic regurgitation, but the change in ejection fraction with exercise by itself is not.