Exercise-induced electrocardiographic changes in patients with chronic respiratory diseases: differential diagnosis...

Evaluation of possible cardiac complications is essential for safe and effective respiratory rehabilitation of patients with chronic respiratory diseases (CRDs). The aim of this study is to clarify the pathophysiology of electrocardiographic (ECG) changes during exercise and the prevalence of coronary artery disease (CAD) in CRD patients without a history of myocardial ischemia.

We studied 42 CRD patients with exercise-induced ST depression by cardiopulmonary exercise testing (CPET). They were selected from 249 consecutive CRD patients without any history of CAD who underwent CPET between January 1999 and December 2001. Thirty-three patients without respiratory diseases who had positive ST depression during exercise were selected as disease control subjects. Exercise myocardial SPECT was performed to evaluate myocardial ischemia and right ventricular (RV) overload as measured by increased RV uptake.

Among the 249 consecutive CRD patients without any history of CAD, positive ST depression during exercise was found in 42 (16.9%). Only 2 of the 42 patients (4.8%) had an ST depression other than in II, III, or aVF leads. The incidence of myocardial ischemia by perfusion SPECT was significantly lower in CRD patients (26.2%) than in disease control subjects (78.8%). The most common finding in the CRD patients during exercise was RV overload but without ischemia (26 cases; 61.9%). Ischemia was found in 11 patients (26.2%), with 10 of these patients also having RV overload. Neither ischemia nor RV overload was found in 5 patients (11.9%); these patients were eventually diagnosed as normal.

The incidence of myocardial ischemia as determined by perfusion SPECT was low in CRD patients with positive exercise-induced ECG changes. On the other hand, RV overload was observed in most such cases. Cardiac perfusion SPECT is a useful technique to evaluate cardiac ischemia and RV overload simultaneously. CPET with 12-lead ECG monitoring is necessary in CRD patients before respiratory rehabilitation. Further examination for ischemia should be done if positive ST depression is found.