Symptom-limited Supine Bicycle Exercise Research Articles

Abstract 16916: Shortening of Pressure Half Time During Exercise as a Predictor for Exercise Capacity in Patients With Bileaflet Mitral Valve Replacement

Introduction: In patients with mechanical mitral valve replacement (MVR), effective orifice area is fixed during dynamic exercise. Therefore, pressure half time (PHT) change during exercise might be mainly influence by exercise-induced left ventricular end-diastolic pressure raise. Hypothesis: We hypothesized that shortening of PHT during supine bicycle exercise would predict exercise capacity in patients with bileaflet mechanical MVR. Methods: Patients with isolated bileaflet MVR (n = 40) prospectively underwent symptom-limited supine bicycle exercise testing with Doppler echocardiography. Heart rate (HR), peak and mean transprosthetic gradient, PHT, and systolic pulmonary artery pressure (SPAP) were assessed at different stages of exercise. Changes in PHT during 25W and 50W exercise (ΔPHT-25W and ΔPHT-50W, respectively) were measured. Changes in HR during 25W and 50W exercise (ΔHR-25W and ΔHR-50W, respectively) were calculated. Results: There were significant negative correlations between exercise duration and ΔPHT-25W (r = -0.345, p = 0.032) or ΔPHT-50W (r = -0.369, p = 0.027) ( Figure A and B ). Exercise duration demonstrated independent significant correlation with both ΔPHT-25W (p = 0.018) and ΔPHT-50W (p = 0.006), even after adjusting for age, sex, and ΔHR-25W/50W, respectively. Conclusion: Degree of PHT shortening during 25W and 50W exercise predicted exercise capacity in patients with bileaflet mechanical MVR. More shortened PHT during exercise was associated with low exercise capacity, which might be associated with diastolic dysfunction resulted from exercise-induced left ventricular end-diastolic pressure raise.

Impact of atrial fibrillation on rest and exercise haemodynamics in heart failure with mid‐range and preserved ejection fraction

Heart failure with preserved (HFpEF) and mid-range ejection fraction (HFmrEF) are becoming the most prevalent forms of heart failure. Patients with HFpEF/HFmrEF in atrial fibrillation (AF) have poorer survival and quality of life, but the mechanism underpinning this is unknown. We sought to investigate the influence of AF on the haemodynamic profile of HFpEF/HFmrEF patients at rest and during exercise. We invasively measured central haemodynamics at rest and during symptom-limited supine bicycle exercise in HFpEF/HFmrEF patients, 35 in sinus rhythm and 20 in AF with matched left ventricular ejection fraction. At rest, AF patients had significantly increased pulmonary capillary wedge pressure, lower cardiac index and reduced left ventricular stroke work index, despite similar resting heart rate. Under resting conditions, calculated oxygen consumption and systemic arteriovenous oxygen gradient were not different between the two groups. During supine cycling at similar levels of workload, AF patients exhibited a reduced capacity to increase their oxygen consumption and this was accompanied by a persistently impaired cardiac index and left ventricular stroke work index. The adverse interaction of AF and HFpEF/HFmrEF may be accounted for by an adverse impact on left ventricular systolic function and peripheral oxygen kinetics.

Effective Orifice Area during Exercise in Bileaflet Mechanical Valve Prostheses

The aims of this study were to investigate the evolution of the transprosthetic pressure gradient and effective orifice area (EOA) during dynamic bicycle exercise in bileaflet mechanical heart valves and to explore the relationship with exercise capacity. Patients with bileaflet aortic valve replacement (n=23) and mitral valve replacement (MVR; n=16) prospectively underwent symptom-limited supine bicycle exercise testing with Doppler echocardiography and respiratory gas analysis. Transprosthetic flow rate, peak and mean transprosthetic gradient, EOA, and systolic pulmonary artery pressure were assessed at different stages of exercise. EOA at rest, midexercise, and peak exercise was 1.66±0.23, 1.56±0.30, and 1.61±0.28cm2, respectively (P=.004), in aortic valve replacement patients and 1.40±0.21, 1.46±0.27, and 1.48±0.25cm2, respectively (P=.160), in MVR patients. During exercise, the mean transprosthetic gradient and the square of transprosthetic flow rate were strongly correlated (r=0.65 [P<.001] and r=0.84 [P<.001] for aortic valve replacement and MVR, respectively), conforming to fundamental hydraulic principles for fixed orifices. Indexed EOA at rest was correlated with exercise capacity in MVR patients only (Spearman ρ=0.68, P=.004). In the latter group, systolic pulmonary artery pressures during exercise were strongly correlated with the peak transmitral gradient (ρ=0.72, P<.001). In bileaflet mechanical valve prostheses, there is no clinically relevant increase in EOA during dynamic exercise. Transprosthetic gradients during exercise closely adhere to the fundamental pressure-flow relationship. Indexed EOA at rest is a strong predictor of exercise capacity in MVR patients. This should be taken into account in therapeutic decision making and prosthesis selection in young and dynamic patients.

Mitral Valve Area During Exercise After Restrictive Mitral Valve Annuloplasty: Importance of Diastolic Anterior Leaflet Tethering

BackgroundRestrictive mitral valve annuloplasty (RMA) for secondary mitral regurgitation might cause functional mitral stenosis, yet its clinical impact and underlying pathophysiological mechanisms remain debated. ObjectivesThe purpose of our study was to assess the hemodynamic and clinical impact of effective orifice area (EOA) after RMA and its relationship with diastolic anterior leaflet (AL) tethering at rest and during exercise. MethodsConsecutive RMA patients (n = 39) underwent a symptom-limited supine bicycle exercise test with Doppler echocardiography and respiratory gas analysis. EOA, transmitral flow rate, mean transmitral gradient, and systolic pulmonary arterial pressure were assessed at different stages of exercise. AL opening angles were measured at rest and peak exercise. Mortality and heart failure readmission data were collected for at least 20 months after surgery. ResultsEOA and AL opening angle were 1.5 ± 0.4 cm2 and 68 ± 10°, respectively, at rest (r = 0.4; p = 0.014). EOA increased significantly to 2.0 ± 0.5 cm2 at peak exercise (p < 0.001), showing an improved correlation with AL opening angle (r = 0.6; p < 0.001). Indexed EOA (EOAi) at peak exercise was an independent predictor of exercise capacity (maximal oxygen uptake, p = 0.004) and was independently associated with freedom from all-cause mortality or hospital admission for heart failure (p = 0.034). Patients with exercise EOAi <0.9 cm2/m2 (n = 14) compared with ≥0.9 cm2/m2 (n = 25) had a significantly worse outcome (p = 0.048). In multivariate analysis, AL opening angle at peak exercise (p = 0.037) was the strongest predictor of exercise EOAi. ConclusionsIn RMA patients, EOA increases during exercise despite fixed annular size. Diastolic AL tethering plays a key role in this dynamic process, with increasing AL opening during exercise being associated with higher exercise EOA. EOAi at peak exercise is a strong and independent predictor of exercise capacity and is associated with clinical outcome. Our findings stress the importance of maximizing AL opening by targeting the subvalvular apparatus in future repair algorithms for secondary mitral regurgitation.

Abstract 19570: Diastolic Anterior Leaflet Tethering Contributes to Functional Mitral Stenosis after Restrictive Mitral Valve Annuloplasty

Introduction: Restrictive mitral valve annuloplasty (RMA) for secondary mitral regurgitation (MR) might cause functional (mitral) stenosis, yet underlying pathophysiological mechanisms remain debated. Hypothesis: Diastolic restriction of the anterior leaflet (AL) opening, due to papillary muscle tethering, plays a key role in the inflow obstruction after RMA. Increasing AL opening during exercise is associated with greater mitral valve area (MVA). Methods: Consecutive RMA patients (n=39, 63±11 years, 77% male) performed a symptom-limited (supine) bicycle exercise test with stepwise Doppler echocardiography and respiratory gas analysis. Diastolic AL opening angle (3-chamber view, Figure A), transmitral flow rate, mean transmitral gradient, and effective MVA were assessed at rest and during peak exercise. Results: At rest, effective MVA (1.5±0.4cm2) correlated moderately to the AL opening angle (68±10°) (r=0.4, p=0.014; Figure B). During exercise, effective MVA increased significantly to 2.0±0.5cm2 (p&lt;0.001), with a stronger correlation to AL opening angle (r=0.6, p&lt;0.001; Figure B). After stratification of the population into tertiles according to increase in AL opening angle during exercise (&lt;=0°, 0-4° and &gt;4° AL angle increase, respectively), a higher increase was significantly associated with greater effective MVA during exercise (p=0.013, Figure C). Patients with AL opening angle &lt;69° at rest (median) and without dynamic AL angle increase of &gt;4° (n=13) had a significantly lower maximal oxygen uptake compared to patients with AL opening angle at rest above the median or a greater dynamic AL angle increase with exercise (n=22) (VO2max 12.5±2.8 versus 16.4±4.7 mL/kg/min, p=0.005). Conclusions: Diastolic restriction of AL opening plays a key role in functional mitral stenosis after RMA for secondary MR. Increasing AL opening at rest, or better AL opening reserve during exercise, are associated with higher MVA and improved exercise capacity.

Effect of exercise and pump speed modulation on invasive hemodynamics in patients with centrifugal continuous-flow left ventricular assist devices

Continuous-flow left ventricular assist devices (CF-LVADs) improve functional capacity in patients with end-stage heart failure. Pump output can be increased by increased pump speed as well as changes in loading conditions. The effect of exercise on invasive hemodynamics was studied in two study protocols. The first examined exercise at fixed pump speed (n = 8) and the second with progressive pump speed increase (n = 11). Patients underwent simultaneous right-heart catheterization, mixed venous saturation, echocardiography and mean arterial pressure monitoring. Before exercise, a ramp speed study was performed in all patients. Patients then undertook symptom-limited supine bicycle exercise. Upward titration of pump speed at rest (by 11.6 ± 8.6% from baseline) increased pump flow from 5.3 ± 1.0 to 6.3 ± 1.0 liters/min (18.9% increase, p < 0.001) and decreased pulmonary capillary wedge pressure (PCWP; 13.6 ± 5.4 to 8.9 ± 4.1 mm Hg, p < 0.001). Exercise increased pump flow to a similar extent as pump speed change alone (to 6.2 ± 1.0 liters/min, p < 0.001), but resulted inincreased right- and left-heart filling pressures (right atrial pressure [RAP]: 16.6 ± 7.5 mm Hg, p < 0.001; PCWP 24.8 ± 6.7 mm Hg, p < 0.001). Concomitant pump speed increase with exercise enhanced the pump flow increase (to 7.0 ± 1.4 liters/min, p < 0.001) in Protocol 2, but did not alleviate the increase in pre-load (RAP: 20.5 ± 8.0 mm Hg, p = 0.07; PCWP: 26.8 ± 12.7 mm Hg; p = 0.47). Serum lactate and NT-proBNP levels increased significantly with exercise. Pump flow increases with up-titration of pump speed and with exercise. Although increased pump speed decreases filling pressures at rest, the benefit is not seen with exercise despite concurrent up-titration of pump speed.

Overweight and Its Association With Aortic Pressure Wave Reflection After Exercise

Obesity is associated with arterial stiffening, left ventricular (LV) hypertrophy, and diastolic dysfunction. However, there is no data regarding dynamic changes in arterial hemodynamics with exercise in overweight subjects. We hypothesized that overweight women would show a different exercise response in wave reflection compared with lean women. A total of 59 overweight and 68 lean nondiabetic women (mean age 63 ± 7 years) underwent symptom-limited supine bicycle exercise testing with simultaneous two-dimensional and Doppler echocardiography. Central hemodynamics including central aortic pressure and augmentation index (AIx) were obtained at rest and immediately after peak exercise using radial artery tonometry. Overweight women showed a higher LV mass index (lean vs. overweight; 40.2 ± 10.2 vs. 45.3 ± 11.0 g/m(2.7), P = 0.007) and a lower early diastolic mitral annular velocity (6.3 ± 1.8 vs. 5.5 ± 1.6 cm/s, P = 0.013) than lean women. Although the two groups did not differ in peripheral and central hemodynamics including AIx (36.3 ± 11.7 vs. 36.8 ± 10.2%, P = 0.830) and AIx normalized for heart rate 75/min (AIx@75, 30.4 ± 11.5 vs. 30.1 ± 9.9%, P = 0.885) at rest, AIx (20.9 ± 11.5 vs. 27.6 ± 10.4%, P = 0.004) and AIx@75 (25.8 ± 10.2 vs. 31.6 ± 7.7%, P = 0.002) at peak exercise were significantly higher in overweight women. In simple correlation analysis, body mass index (BMI) showed significant correlations with AIx, and AIx@75 at peak exercise, whereas no relationships were found with those parameters at rest. Multiple regression analysis showed that BMI was an independent determinant of AIx@75 at peak exercise (β = 0.28, P = 0.004). Despite similar resting peripheral and central hemodynamics, the wave reflection in overweight women after exercise differed from that in lean women. These findings suggest that being overweight is related to higher wave reflection after exercise.

Characteristics of Exercise‐Induced Intrapulmonary Arteriovenous Fistula in Patients with Unexplained Exertional Dyspnea

Dynamic appearance of intrapulmonary arteriovenous fistula (AVF) during exercise may be associated with unexplained exertional dyspnea (UED) and can be diagnosed with an agitated saline contrast study during exercise echocardiography. However, the occurrence of AVF during exercise in patients with UED has not been well described. Thus, the frequency of exercise-induced intrapulmonary AVF in the outpatients with UED was retrospectively analyzed. Thirty-nine outpatients (age: 53 ± 12, 33 female) with UED underwent symptom-limited supine bicycle exercise echocardiography. Ten patients (26%) developed exercise-induced intrapulmonary AVF. Patients with and without AVF showed the similar peak exercise heart rate, systolic blood pressure, and rate-pressure product. The patients with AVF demonstrated a small but significant decrease in arterial oxygen saturation with exercise as compare to baseline (95.6 ± 2.8% at peak, vs. 97.5 ± 2.5% at baseline, P < 0.05 with a paired Student t-test). Our study suggests that exercise-induced intrapulmonary AVF is relatively common in the outpatients with UED and associated with mild exercise desaturation; however, the mechanism of desaturation could not be determined by this study. Further investigation to characterize and determine the clinical significance of AVF is warranted.

Abstract 2207: Value of Ventricular Stiffness Index and Ventricular-Arterial Interaction in Predicting Exercise Capacity in Patients with Nonischemic Dilated Cardiomyopathy

Increased ventricular stiffness and afterload are major contributors to the pathogenesis of heart failure. We sought to investigate whether dilated cardiomyopathy (DCM) patients have distinct ventricular elastance or ventricular-arterial interaction compared to hypertensive patients or healthy controls and they can be used to predict exercise capacity. Twenty-five patients with DCM, 25 age- and gender-matched hypertensive patients, and 25 healthy controls underwent a symptom-limited graded supine bicycle exercise echo after a comprehensive resting echo-Doppler evaluation. Left ventricular (LV) diastolic elastance (Ed, early mitral inflow to anuular velocity/stroke volume), ventricular-vascular coupling index (VVI, Ea/Ees) based on arterial elastance index (Ea, end-systolic pressure/stroke volume) to LV end-systolic elastance index (Ees, peak LV outflow tract velocity to acceleration time) and hemodynamic parameters were measured during exercise test. DCM patients had lower Ees, and higher Ed and VVI with blunted response of Ees and Ea to peak exercise than hypertensive patients or controls. In DCM patients, resting Ees correlated with contractile reserve to low grade exercise (Δsystolic mitral annular velocity to 25W. r=0.561, p=0.004) with close relationship between Ed and VVI (r=0.525, p=0.007 at rest; r=0.510, p=0.047 at 25W exercise). Resting Ed (β=−0.597, p=0.003), VVI (β=−0.523, p=0.010), and total stiffness index (Ed x VVI, β=−0.647, p=0.001) correlated with exercise duration independent of age and gender. Total stiffness index could reliably predict the impaired exercise capacity (&lt;400 sec, 69% sensitivity and 70% specificity). DCM patients have distinct Ed and VVI, which have mutual relationship and predictive power of exercise capacity.

Biphasic relaxation-frequency relations in patients with effort angina pectoris: a new marker of myocardial demand ischemia

Background Relaxation-frequency relations (RFR) during demand ischemia have not been fully examined in patients with effort angina pectoris (AP). We sought to clarify the effects of pacing and exercise on RFR in patients with AP. Methods We recorded left ventricular (LV) pressures during rapid atrial pacing and symptom-limited supine bicycle exercise. RFR were analyzed in 24 patients with AP and 10 controls. Results LV pressure half-time (T 1/2) in controls was gradually shortened with an increase in heart rate (HR) during pacing (−19% ± 6% at peak HR). The changes in T 1/2 during pacing were biphasic with initial shortening (−12% ± 5% at the critical HR) followed by prolongation (−3% ± 7% at peak HR) in all patients with AP. The critical HR, at which T 1/2 was minimum, preceded the HR at 0.1-mV ST-segment depression, and finally chest pain occurred. The critical HR was correlated negatively with the severity of ischemia as assessed by thallium-201 scintigraphy. T 1/2 was remarkably shortened during exercise in controls (−41% ± 10% at peak exercise). In patients with AP, 2 distinct patterns of RFR were observed during exercise. T 1/2 was shortened progressively (−37% ± 8% at peak exercise) in 15 patients, whereas RFR remained biphasic (−21% ± 10% at the critical HR and −11% ± 11% at peak exercise) in the other 9 patients. Coronary angiography and exercise scintigraphy suggested more severe ischemia in patients with biphasic RFR during exercise. Conclusions Impaired RFR might be the most sensitive parameter of pacing-induced ischemia. The critical HR was closely related with severity of ischemia. Adverse effects of ischemia on LV relaxation may be alleviated by exercise.

Biphasic changes in left ventricular end-diastolic pressure during dynamic exercise in patients with nonobstructive hypertrophic cardiomyopathy

OBJECTIVES The aim of this study was to clarify the serial changes in left ventricular (LV) end-diastolic pressure (LVEDP) during dynamic exercise in patients with hypertrophic cardiomyopathy (HCM). BACKGROUND Although HCM is characterized by impaired resting LV diastolic function, serial changes in LVEDP during exercise have not been characterized. METHODS We simultaneously measured LV pressure and LV dimensions during symptom-limited supine bicycle exercise in 5 healthy individuals and 20 patients with HCM. Exercise thallium-201 scintigraphic studies were also performed. RESULTS The LVEDP (baseline: 12 ± 5 mm Hg) progressively increased to a maximum value at peak exercise (28 ± 8 mm Hg) in 11 patients with HCM (group I). In the remaining nine patients with HCM (group II), changes in LVEDP during exercise were biphasic, with an initial progressive increase and a subsequent gradual decline up to peak exercise (14 ± 4 mm Hg at baseline, 27 ± 5 mm Hg at the critical heart rate, 16 ± 3 mm Hg at peak exercise). Exercise-induced changes in LV dimensions and LV peak systolic pressures were similar in both groups. However, the maximum first derivative of LV pressure was greater and the LV pressure half-time was shorter in group II than in group I at a similar peak exercise heart rate. The biphasic changes in LVEDP disappeared by pretreatment with propranolol. The LV hypertrophy scores were higher in group I than in group II. Exercise thallium-201 images showed more severe perfusion defects in group I than in group II patients. CONCLUSIONS The biphasic changes in LVEDP seen during exercise may be related to improved coronary microcirculation in response to beta-adrenergic stimulation in patients with mild to moderate HCM.

Attenuated Responses of Doppler-Derived Hemodynamic Parameters during Supine Bicycle Exercise in Heart Transplant Recipients

The aim of this study was to characterize Doppler-derived hemodynamic parameters in heart transplant recipients at rest and during symptom-limited supine bicycle exercise. Eighteen sedentary patients aged 54.0 ± 2 years, 1.6 ± 1.0 years following cardiac transplantation, and 18 sedentary healthy volunteers aged 51.8 ± 4 years were investigated. Basic hemodynamic parameters and Doppler-derived parameters were recorded at rest and at peak dynamic exercise. Resting heart rate, blood pressure and rate-pressure product were higher in the transplanted patients (p < 0.001). However, in comparison with the resting state, the increase in these parameters at exercise was lower in heart transplant recipients. In the healthy, dynamic exercise induced an increase in peak flow velocity, mean acceleration, flow velocity integral, stroke volume, cardiac output and cardiac index (p < 0.001 for all) while systemic vascular resistance, ejection time and acceleration time decreased (p < 0.001 for all). The following parameters increased in the transplanted patients at dynamic exercise: peak flow velocity, cardiac output and cardiac index (p < 0.001), mean acceleration (p < 0.01) and flow velocity integral (p < 0.05). Ejection time decreased (p < 0.05) and acceleration time and systemic vascular resistance remained unchanged. In conclusion, at rest peak flow velocity, mean acceleration, flow velocity integral and stroke volume are lower in the transplanted than in the healthy controls, while cardiac output, cardiac index and systemic vascular resistance are equal. Our study demonstrates attenuated responses of basic hemodynamic parameters and Doppler-derived cardiovascular indices at symptom-limited supine bicycle exercise in heart transplant recipients compared to healthy volunteers.

941-22 Role of Dynamic Changes in Left Ventricular Function in Determining Exercise Capacity in Patients with Nonobstructive Hypertrophic Cardiomyopathy

Measurements of LV morphology and function at rest predict weakly exercise capacity in hypertrophic cardiomyopathy (HC). Aim of this study was to verify whether dynamic changes in LV function relate to exercise duration in HC. Accordingly, we studied 25 patients, off-drugs, with nonobstructive HC (15 males, aged 43 ± 13 yrs). who undervvent baseline Doppler echocardiography, cardiac catheterization, and symptom-limited supine bicycle exercise (25 watt/2 mins) with postexercise Doppler echocardiography. Exercise capacity ranged from 50 to 125 (mean: 79 ± 27) watts. No relation was found between exercise time and indices of LV morphology (i.e. maximal wall thickness, wall thickness index, end-diastolic and end-systolic dimensions). or function at rest (i.e. LV ejection fraction, stroke volume index, right- and left-sided intracavitary pressures, Doppler indices of LV diastolic filling). In contrast, exercise capacity correlated significantly (p &lt; 0.01) with the magnitude of changes recorded at peak exercise in ejection fraction (r = 0.65). LV end-diastolic volume (r = 0.67), and Doppler peak early filling velocity (r = 0.60). Change in ejection fraction related significantly (p &lt; 0.01) to change from baseline in both LV end-diastolic volume (r = 0.71) and peak early filling velocity(r = 0.55). Multiple regression analysis revealed that the response of ejection fraction to exercise was the strongest predictor of exercise capacity (p = 0.001). Noteworthy, 10/25 patients exhibited the lack of stress-induced increase in ejection fraction. We conclude that in nonobstructive HC: (1) dynamic changes in LV function correlate with exercise duration; (2) indices of LV morphology and function at rest do not predict exercise capacity; (3) exercise intolerance seems to be caused by worsening in diastolic filling, leading to the inability to increase LV volume with exercise to maintain systolic function.

Markers of left ventricular dysfunction induced by exercise, dipyridamole or combined stress on ECG-gated myocardial perfusion scans.

An index of left ventricular contraction can be extracted from the cavitary time-activity curve of electrocardiographic (ECG)-gated myocardial perfusion scans. To assess the induction of stress-induced myocardial depression, we compared contraction indexes derived from immediate poststress and delayed 201Tl images with indexes of ventricular dilation and lung uptake in the prediction of severe coronary artery disease (defined as two or more 90% stenoses). Stress procedures were performed in 93 patients with symptom-limited supine bicycle exercise alone, and in 227 with intravenous dipyridamole, combined where possible with exercise. The immediate and delayed contraction indexes reflected left ventricular dysfunction on ventriculography (P < 0.0001), but additionally the immediate index was reduced (P < 0.0001) in severe coronary disease. Stress-induced hypokinesis was seen frequently after each of the test modes. The relationship with angiographic findings was better defined for indexes of contraction than for lung uptake or ventricular dilation (P < 0.01). The prediction of severe coronary disease was optimized by combining the poststress contraction index and lung uptake. These data support the use of ECG-gated myocardial scans in evaluating the functional consequences of stress/imaging procedures.

Abnormal vascular responses to supine exercise in hypertrophic cardiomyopathy.

Exercise hypotension has been documented in hypertrophic cardiomyopathy. It is not the result of an inability to augment cardiac output but instead relates to an inappropriate and exaggerated decrease in systemic vascular resistance at high work loads. To enable us to examine the behavior of the peripheral vasculature during exercise, 103 consecutive patients underwent maximal symptom-limited supine bicycle exercise with measurement of forearm blood flow. A minimum reduction of 12% from the basal value was defined as a normal response based on the study of 25 normal controls. In the patients, two patterns of forearm blood flow were observed. Sixty-four patients had an appropriate reduction in forearm blood flow of 40 +/- 16% from resting flow. In 39 patients, the forearm blood flow either failed to decrease or increased with exercise by 45 +/- 105% of the resting value. Patients with an abnormal forearm vasodilator response were younger (31 +/- 13 versus 46 +/- 14 years), and more of them had a family history of hypertrophic cardiomyopathy and sudden death than did those with a normal vasoconstrictor response (16 of 39 versus eight of 64). Left ventricular end-diastolic cavity dimensions were smaller in those with an abnormal forearm blood flow response, but other clinical, echocardiographic, and arrhythmic variables were similar. To assess the relation of abnormal peripheral vascular responses to erect exercise blood pressure response, patients underwent treadmill exercise testing with careful monitoring of systolic blood pressure response. Thirty-eight patients had significant exercise hypotension with failure of the systolic blood pressure to increase during progressive exercise (n = 6) or an abrupt decrease in systolic blood pressure (20-60 mm Hg) from the peak value (n = 32); 65 patients had a normal exercise blood pressure response, but 18 of these patients had an oscillation in systolic blood pressure of 10 mm Hg or more early in the recovery phase. Thirty-one of 39 patients with an abnormal forearm blood flow response demonstrated exercise hypotension during the erect exercise testing, and the remaining eight patients had a normal exercise blood pressure response; however, five of these eight had abnormal oscillations in blood pressure during recovery (r = 0.61, p less than 0.001). The relation of abnormal peripheral vascular responses to exercise hypotension confirms the observation of hemodynamic instability in patients with hypertrophic cardiomyopathy. The finding of abnormal vascular responses in patients known to be at increased risk (young age and a family history of hypertrophic cardiomyopathy and sudden death) suggests that hemodynamic mechanisms may be important in the occurrence of sudden death in hypertrophic cardiomyopathy.

Stability of Pacing Threshold, Impedance, and R Wave Amplitude at Rest and During Exercise

The pacing threshold of the human heart may be altered by physiological factors such as physical exercise. These changes may influence the individual programming of a pacemaker, since pacemakers can be programmed at pulse amplitudes of 2.5 volts and less. We investigated 22 patients with a multiprogrammable ventricular demand pacemaker 3 months after implantation; 16 patients had received a steroid-eluting lead and six patients had an Elgiloy lead. Parameters measured at rest and immediately after exercise were: Voltage threshold at pulse durations between 0.05 and 0.6 ms, impedance, R wave amplitude and energy consumption for the pacing threshold at 0.5 ms pulse duration. All patients performed a symptom limited supine bicycle exercise test. None of the investigated parameters showed a significant difference between rest and exercise, neither for the steroid eluting lead nor for the Elgiloy lead. The data suggest that the individual programming of a pacemaker adapted to the measurements at rest is also reliable and safe during exercise.

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.

Reduced exercise capacity of chronic obstructive pulmonary disease patients exercising with noseclip/mouthpiece

A noseclip and low resistance mouthpiece are often used to monitor exhaled gases during exercise. Because otolaryngologic studies suggest that 50% of airway resistance is in the nose and mouth, it was hypothesized that patients with advanced chronic obstructive pulmonary disease might be artifactually limited by exercise testing with a noseclip and mouthpiece. Accordingly, 12 patients with stable chronic obstructive pulmonary disease performed identical symptom-limited supine bicycle exercise tests with and without noseclip and mouthpiece. Right-sided cardiac hemodynamic measurements, radionuclide ventriculography and arterial and mixed venous gas sampling were performed during each exercise test. Exhaled gases were analyzed during the noseclip/mouthpiece exercise. The order of exercise tests was alternated. Comparing exercises with and without a noseclip, there were significant reductions in exercise duration (397 ± 270 vs 300 ± 230 seconds, p < 0.01), exercise oxygen consumption (780 ± 279 vs 638 ± 200 ml/min, p < 0.01) and exercise cardiac output (8.4 ± 2.7 vs 7.3 ± 2.0 liters/min, p < 0.05), an increase in right ventricular ejection fraction (0.39 ± 0.08 vs 0.43 ± 0.08, p < 0.01) and no change in exercise heart rate (106 ± 14 vs 106 ± 14), right-sided cardiac pressures or arterial and mixed venous blood gases. These data suggest that a noseclip/mouthpiece can limit exercise tolerance in advanced chronic obstructive pulmonary disease patients. This limitation may result from decreased right-sided cardiac preload (venous return).

Doppler echocardiography and ultrafast cine computed tomography during dynamic exercise in chronic parenchymal pulmonary disease

In an effort to better understand the cardiac contribution to exercise limitation in chronic lung disease, 21 patients with advanced chronic pulmonary parenchymal disease and 10 normal control subjects were evaluated for changes in right ventricular (RV) pressure, volume and function during incremental, symptom-limited supine bicycle exercise. Patients underwent sequential exercise tests with Doppler echocardiography and ultrafast cine computed tomography (CT). RV systolic pressure during exercise was determined by saline-enhanced Doppler of tricuspid regurgitation. RV ejection fraction, end-diastolic volume, stroke volume and cardiac index were obtained by CT at rest and peak exercise. Sixteen of the 21 study patients also exercised on high-flow oxygen. In the control subjects RV systolic pressure increased from 21 ± 6 mm Hg (mean ± standard deviation) at rest to 32 ± 8 mm Hg at peak exercise, whereas in patients with lung disease, RV systolic pressure increased from 42 ± 17 to 81 ± 26 mm Hg (both p < 0.01). Compared with the control subjects, the patients with lung disease had significantly lower mean values for RV ejection fraction at rest (47 ± 7 vs 55 ± 7%) and at peak exercise (47 ± 9 vs 57 ± 3%, respectively, both p < 0.05). The patients who demonstrated oxyhemoglobin desaturation during exercise showed the most abnormal cardiac responses, with marked increases in mean RV systolic pressure, decreases in mean RV ejection fraction and blunted increases in cardiac index and RV stroke volume. Although acute oxygen supplementation was associated with a slight decrease in RV systolic pressure at peak exercise and a longer duration of exercise, there was no significant improvement in RV function. Doppler echocardiography and CT provide complementary and potentially useful information about right-sided heart pressures and RV ejection fraction during exercise in patients with advanced chronic lung disease. Oxyhemoglobin desaturation during exercise is a marker for the most abnormal pulmonary vascular reserve, as indicated by RV contractile dysfunction and limited ability to increase cardiac index.

Phase and amplitude analysis of exercise digital left ventriculograms in patients with coronary disease.

Phase and amplitude analysis was applied to intravenous digital left ventriculograms to avoid the artefacts associated with image subtraction. Eight controls and 40 patients with known coronary artery disease underwent digital left ventriculography before and after a symptom limited supine bicycle exercise test. The resultant images were subjected to phase and amplitude analyses. In the control group there was no deterioration in left ventricular wall motion after exercise. In 30 of the 40 patients there was a deterioration in wall motion on exercise. This group contained all eight patients with three vessel disease and 12 of the 17 patients with two vessel disease. Ten patients showed no change in wall motion--five with one vessel disease and five with two vessel disease. Phase and amplitude analysis of digital left ventriculograms is a method of detecting exercise induced myocardial ischaemia that may help in the assessment of patients with coronary artery disease.