Takesatoru Fukuda

Adequacy of Pacing Rate During Exercise in Rate Responsive Ventricular Pacing

Our objective was to determint; the adequate pacing rate during exercise in ventricular pacing by measuring exercise capacity, cardiac output, and sinus node activity. Eighteen patients with complete AV block and an implanted pacemaker underwent cardiopulmonary exercise tests under three randomized pacing rates: fixed rate pacing (VVJ) at 60 beats/min and ventricular rate‐responsive pacing (VVIR) programmed to attain a heart rate of about 110 beats/min ar 130 beats/min (VVIR 110 and VVIR 130, respectively) at the end of exercise. Compared with VVI and VVIR 130, VVIR 110 was associated with an increased peak oxygen uptake(VVIR 110:20.3 ± 4.5 vs VVI: 16.9 ± 3.1; P < 0.01; and VVIR 130: 19.0 ± 4.1 mL/min per kg, respectively; P < 0.05) and a higher oxygen uptake at anaerobic threshold (15.3 ± 2.7, 12.7 ± 1.9; P < 0.01, and 14.6 ± 2.6 mL/min per kg; P < 0.05). The atrial rate during exercise expressed as a percentage of the expected maximal heart rate was lower in VVIR 110 than in VVI or VVIR 130 (VVIR 110: 75.9%± 14.6% vs VVI: 90.6%± 12.8%; P < 0.01; VVIR 110 vs VVIR 130: 89.1%± 23.1%; P < 0.05). There was no significant difference in cardiac output at peak exercise between VVIR 110 and VVIR 130. We conclude that a pacing rate for submaximal exercise of 110 beats/min may be preferable to that of 130 beats/min in respect to exercise capacity and sympathetic nerve activity.

Effects of enalapril on cardiac function, exercise capacity, and biochemical factors in patients with chronic heart failure

Abstract The angiotensin-converting enzyme (ACE) inhibitor enalapril was administered to 13 patients with chronic heart failure (New York Heart Association class II or III) for 12 weeks, and its effects on resting cardiac function (shown by echocardiogram), exercise capacity, and biochemical factors were investigated. Left ventricular end-diastolic and end-systolic diameters improved significantly from 60.3 ± 5.4 mm at baseline to 57.2 ± 5.7 mm after 12 weeks of treatment and from 50.2 ± 5.9 mm to 46.8 ± 5.6 mm, respectively; however left atrial dimension did not change significantly after treatment. Peak oxygen uptake also improved significantly after enalapril treatment (20.0 ± 6.9 mL/kg/min at baseline to 22.4 ± 7.6 mL/kg/min after treatment), as did anaerobic threshold by gas exchange (17.1 ± 6.4 mL/kg/min vs 18.4 ± 5.8 mL/kg/min). The serum levels of atrial natriuretic peptide and beta-endorphin decreased significantly after treatment (47.6 ± 42.1 pg/mL before vs 31.6 ± 29.2 pg/mL after treatment and 11.6 ± 3.6 pg/mL vs 5.9 ± 2.8 pg/mL, respectively). These results indicated that enalapril is useful for improving resting cardiac function, exercise capacity, and biochemical factors in patients with chronic heart failure.