Systemic Peripheral Vascular Resistance as a Determinant of Functional Cardiac Reserve in Response to Exercise in Patients With Heart Disease

Resting cardiac function is a poor indicator of functional cardiac reserve that is invoked during exercise. The objective of this study was to investigate the relationship between functional cardiac reserve and systemic vascular resistance (SVR) using an ambulatory radionuclide monitoring system (the Vest system) in patients with heart disease. The study population consisted of 29 patients (all male [mean ± SD age, 63 ± 10 years]), 23 with coronary artery disease, 3 with dilated cardiomyopathy, and 3 with hypertensive heart disease. All patients underwent cardiopulmonary stress testing using a ramped treadmill protocol and the Vest system. The anaerobic threshold (AT) was autodetermined using the V-slope method. Systemic vascular resistance was calculated using the mean blood pressure and cardiac output as determined using the Vest system parameters. All patients exercised beyond the AT until exhaustion. Resting left ventricular ejection fraction, peak ejection ratio, and peak filling ratio increased with the AT (P < .01 for all). Resting SVR decreased with the AT (P < .01). The percentage changes from rest to the AT in SVR correlated with those from rest to the AT in ejection fraction, peak ejection ratio, and peak filling ratio (r = −0.735, r = −0.510, and r = −0.697, respectively; P < .01). These findings indicate that SVR as recorded using the Vest system is a good determinant of functional cardiac reserve in patients with heart disease. Therefore, cardiopulmonary function testing combined with the Vest system is a good modality for the evaluation of functional cardiac reserve.