Effects of isosorbide dinitrate on electrocardiography, hemodynamics, and ventilation in patients with exercise-induced elevation of pulmonary artery wedge pressure

Abstract

Background: The mechanisms underlying exertional hyperpnea in patients with coronary artery disease and transient left ventricular dysfunction are still not fully understood. Hypothesis: The study was undertaken to investigate whether the ventilatory response to exercise reflects the effects of acute medical treatment of exercise-induced left ventricular dysfunction, and to evaluate mechanisms relevant to excessive exertional ventilation. Methods: In 11 male patients, aged 65.2 ± 6.0 years, all with pulmonary artery wedge pressure (PAWP) > 25 mmHg and ST depression > 2 mm during moderate supine exercise, ventilation (V̇), oxygen uptake (V̇O2), hemodynamics, electrocardiogram (ECG), and arterial and mixed venous blood gases were examined during supine rest and exercise, before and at hourly intervals after peroral intake of 30 mg isosorbide dinitrate (ISDN). Six similar patients were examined with the same protocol without ISDN administration and comprised a control group. Results: Before administration of ISDN, exercise PAWP was 35.3 ± 5.9 mmHg, ECG showed 2.77 ± 1.06 mm ST depression, and V̇/V̇O2 was 31.8 ± 4.81/1. One h after ISDN administration, exercise mean PAWP was 11.0 ± 2.5 mmHg (p < 0.001), ST depression 0.59 ± 0.8 mm (p < 0.001), whereas V̇/V̇O2 was unchanged, 30.1 ± 5.3 1/1. Two h later, PAWP remained reduced and there were only minor ST depressions, while V̇/V̇O2 remained high. Exercise cardiac index (CI) and mixed venous oxygen tension (PvO2), initially 4.7 ± 0.67 1/min/m2 and 3.54 ± 0.35 kPa, respectively, remained at the same low level throughout the study. In the six nontreated patients, there were no significant changes in ST depression, exercise PAWP, or exertional ventilation. Conclusion: Isosorbide dinitrate treatment markedly improved exercise-induced left heart dysfunction, whereas excessive ventilatory response was unaffected, even after 3 h. Thus, measurements of the exercise hyperpnea did not properly reflect effective reduction of myocardial ischemia.