Long-term prognosis of painless exercise-induced ischemia in stable patients with previous myocardial infarction

The Clinical Utility of Cardiopulmonary Exercise Testing in Suspected or Confirmed Myocardial Ischemia

Heart disease is a major cause of morbidity and mortality in the United States, with coronary artery disease (CAD) representing more than half of all cardiovascular events. Stable patients presenting with symptoms suggestive of CAD are likely to undergo an exercise electrocardiogram (ECG) and/ or imaging study as a first-line diagnostic assessment. A cardiopulmonary exercise test (CPX) is an ECG stress test plus ventilatory gas analysis. Recently, CPX has been used to detect exercise-induced myocardial ischemia (EIMI) suggestive of underlying CAD. Two CPX variables, oxygen pulse (VO2/HR) and the slope of oxygen consumption versus work rate (Δ VO2/ Δ WR), have been identified to be especially indicative of EIMI. Currently, there are a number of diagnostic tests available for the identification of CAD, with the most widely used being stress ECG, stress myocardial perfusion imaging (MPI) and echocardiography, and cardiac catheterization. Exercise ECG, although inexpensive, has a number of well-recognized limitations, including low sensitivity resulting in false-negative results. Stress (exercise or pharmaceutically induced) MPI and catheterization are more accurate but also more invasive and expensive. It appears that CPX may improve the diagnostic accuracy of exercise ECG. This review will address the potential utility of CPX in patients with suspected or confirmed myocardial ischemia.

A prospective study of long term prognosis in young myocardial infarction survivors: the prognostic value of angiography and exercise testing

OBJECTIVES

To define the ability of early exercise testing and coronary angiography to predict prognosis in young survivors of myocardial infarction (MI).

METHODS

255 consecutive patients (210 men) aged 55 years or less (mean 48 years) admitted to hospital (1981-85) were eligible. Of these, 150 patients (130 men) who were able to exercise early after MI and underwent coronary angiography within six months constituted the study group and were followed up for up to 15 years. Survival data up to 18 years was obtained for the whole cohort.

RESULTS

Survival at a median of 16 years was 52% for the whole cohort, 62% for the study group, and 48% for the excluded group. From nine years onwards survival deteriorated significantly in the study group compared with an age matched background population. Fifteen years after MI, 121 patients (81%) in the study group had had at least one event (death, MI, revascularisation, cardiac readmission, stroke) leaving 29 (19%) event-free. The number of diseased vessels was the major determinant of time to first event (p = 0.001) and event-free survival (p = 0.04). Exercise duration was also important in the prediction of time to first event (p = 0.003). Death was influenced by a history of prior MI.

CONCLUSION

The favourable initial survival was followed by significant deterioration after nine years. This late attrition is an important treatment target. Furthermore, this study supports risk stratification early after MI combining angiography with non-invasive tools.

Exercise-induced symptomatic ischaemia predicts a poor long-term prognosis after acute myocardial infarction

STUDY OBJECTIVES

To evaluate the long-term prognostic significance of symptomatic ischaemia during exercise testing performed 3 weeks after acute myocardial infarction (AMI).

DESIGN

A prospective study with long-term follow-up.

SETTING

A Cardiac Rehabilitation Clinic in a University Hospital.

SUBJECTS

A total of 446 patients were allowed to perform exercise testing 3 weeks after AMI and followed for 72 +/- 20 months.

MEASUREMENTS AND RESULTS

Patients were divided into three groups according to whether they had no ECG evidence of ischaemia during exercise testing (334 patients), silent ischaemia (90 patients) or symptomatic ischaemia (22 patients). Cardiac death was significantly more frequent in patients with symptomatic ischaemia when compared with silent ischaemia (31.8% vs. 7.8%, P < 0.01) or when compared with no ischaemia (31.8% vs. 10.2%, P < 0.01). The three groups had a low cardiac mortality during the first 48 months of follow-up. The prognosis of patients with symptomatic ischaemia worsens markedly thereafter. The results of exercise testing did not predict recurrence of myocardial infarction. Coronary revascularization was performed in 34.4% of those without ischaemia, 47.8% of those with silent ischaemia and 45.5% of those with symptomatic ischaemia (P < 0.01).

CONCLUSIONS

Patients with symptomatic ischaemia have a good prognosis during the first 4 years of follow-up. Their prognosis worsens thereafter as opposed to patients with or without silent ischaemia. This high-risk group of patients with symptomatic ischaemia deserves optimal management including revascularization when appropriate.

Ten-year mortality rate in relation to observations at a bicycle exercise test in patients with a suspected or confirmed ischemic event but no or only minor myocardial damage: influence of subsequent revascularization

AIM

Our purpose was to describe symptoms and electrocardiographic findings at a bicycle exercise test 4 weeks after hospitalization for a suspected or confirmed acute ischemic event but either no or only minor myocardial necrosis and its relationship to long-term prognosis and subsequent revascularization.

METHODS

In all patients a symptom-limited bicycle exercise test was performed 4 weeks after discharge from the hospital. The total mortality rate over 10 years was registered.

RESULTS

In all, 770 patients participated in the evaluation. The median age was 63 years, and 34% were women. The most frequent reason for stopping the exercise test was fatigue (69%) followed by dyspnea (33%) and angina pectoris (15%). Angina pectoris was observed in 24% of the patients. ST-segment depression >or=1 mm was observed in 50% and ST-segment depression >or=2 mm was observed in 15% of the patients. The 10-year mortality rate in patients with ST-segment depression >or=2 mm was 24.7%, in patients with ST-segment depression 1.0 to 1.9 mm 33.5%, and in patients with ST-segment depression <1 mm 26.9% (not significant [NS]). Patients with symptoms of angina pectoris had a 10-year mortality rate of 29.4% compared with 27.9% among patients without such symptoms (NS). Patients who had either a drop in systolic blood pressure or failure to raise systolic blood pressure (13%) had a 10-year mortality rate of 36.2% compared with 27.2% among patients without such signs (NS). However, there was a significant association between maximum exercise capacity (in watts) and mortality (P < .0001): 53.8% in the lowest quartile (30-70 W) and 10.2% in the highest (>120 w). When clinical history was considered simultaneously, a low exercise capacity remained as a strong independent predictor of death together with age and a history of either acute myocardial infarction, smoking, or diabetes mellitus. Mechanical revascularization during the subsequent 5 years interacted only with angina pectoris and prognosis; thus patients who had angina during the exercise test had a worse prognosis than those without if they were not being revascularized.

CONCLUSION

Among patients hospitalized with a suspected or confirmed acute ischemic event but either no or only minor myocardial necrosis, we found the maximum working capacity at a symptom-limited bicycle exercise test to be independently associated with the long-term prognosis but not other signs of myocardial ischemia. Further predictors for long-term prognosis were age, a history of acute myocardial infarction, current smoking, and diabetes mellitus. Mechanical revascularization during the subsequent 5 years interacted with the influence of symptoms of angina during test and prognosis.