CARDIOPULMONARY EXERCISE RESPONSE IN PATIENTS WITH LEFT-VENTRICULAR DYSFUNCTION OR HEART-FAILURE - A NONINVASIVE STUDY BY GAS-EXCHANGE AND IMPEDANCE CARDIOGRAPHY MONITORING

We investigated the upright bicycle exercise cardiopulmonary response in 20 patients with left ventricular dysfunction (LVD, secondary to pr evious myocardial infarction, left ventricular ejection fraction range 18-44%). Ten patients (48 +/- 7 years) were asymptomatic (I NYHA clas s) without drug treatment (LVD group). The others (n = 10) (50 +/- 1 y ears) complained of dyspnea and/or fatigue despite therapy (NYHA II-II I). They represented the heart failure (HF) group. Eight sedentary men (40 +/- 10 years) served as controls. Controls and patients performed stress testings under drug treatment, when administered. Anaerobic ve ntilatory threshold (ATge) was considered as an index of submaximal ex ercise while peak exercise VO2 (PeakVO(2)) was considered the maximal volitional exercise capacity. The ratio between minute ventilation (VE ) to carbon dioxide release (VCO2) (VE/VCO2) was assessed to evaluate the ventilatory response during exercise. We coupled gas exchange asse ssment (2001, MGC) with noninvasive monitoring of stroke volume (SV) b y impedance cardiography (NCCOM3, BOMED) and total systemic vascular r esistances (TSVR; by auscultatory blood pressure measurement). In cont rols VO2 increase during exercise was related to higher heart rate (HR ) and SV both from resting to ATge and from this point to the peak. TS VR declined during both steps. In patients with HF VO2 rose from resti ng to ATge (by faster HR and unchanged SV). VO2 increased slightly fro m this point to PeakVO(2). This result was related to flat HR increase and unchanged SV as well as TSVR. In patients with LVD VO2 increased similarly to controls from resting to ATge and less above the threshol d. In these patients both HR and SV increased during submaximal exerci se. From ATge to PeakVO(2) only HR increased. TSVR declined significan tly similarly to controls. The VE/VCO2 ratio was higher at peak exerci se in patients with HF compared to controls. Different determinants we re demonstrated in patients with left ventricular dysfunction with mil d or symptomatic chronic heart failure (CHF). These findings and the i ncreased ventilatory response in patients with CHF can explain differe nt changes of VO2 in these patients during submaximal and maximal volu ntary exercise and contribute to explain exercise-induced exertion in these subjects.