Usefulness of exercise testing shortly after acute myocardial infarction for predicting 10-year mortality

Physical Fitness Evaluation

Physical fitness is simply defined as the capacity to perform physical work. Energy is necessary to perform work and sustain life and is extracted aerobically and anaerobically. Evaluation of aerobic fitness is based on the assessment of maximal oxygen consumption (Vo2 max), either directly or indirectly. Direct assessment of Vo2 max is usually determined by a graded exercise test using open circuit spirometry. Indirect assessments of Vo2 max use standardized exercise protocols. Such protocols can also be used to estimate Vo2 max with the subject exercising at submaximal heart rate levels. These estimates are based on the linear relationship between exercise heart rate and O2 consumption. Walking and step tests that allow an estimate of fitness based on exercise and recovery heart rate responses are also available. Evaluation of anaerobic power consists of 30 to 120 seconds of high-intensity effort on a cycle ergometer, known as the Wingate test. Muscular strength is assessed by a maximum effort against the greatest resistance one can move through the full range of motion once, known as the 1-repetition maximum. Muscular endurance is assessed by tests requiring more than 12 repetitions, or the maximum number of push-ups or sit-ups one can execute without rest.

Low exercise blood pressure and risk of cardiovascular events and all-cause mortality: systematic review and meta-analysis

OBJECTIVE

The independent prognostic significance of abnormally low systolic blood pressure (SBP) during exercise stress testing (LowExBP) across different clinical and exercise conditions is unknown. We sought by systematic review and meta-analysis to determine the association between cardiovascular/all-cause outcomes and LowExBP across different patient clinical presentations, exercise modes, exercise intensities and categories of LowExBP.

METHODS

Seven online databases were searched for longitudinal studies reporting the association of LowExBP with risk of fatal and non-fatal cardiovascular events and/or all-cause mortality. LowExBP was defined as either: SBP drop below baseline; failure to increase >10 mmHg from baseline or; lowest SBP quantile among reporting studies.

RESULTS

After review of 13,257 studies, 19 that adjusted for resting SBP were included in the meta-analysis, with a total of 45,895 participants (average follow-up, 4.4 ± 3.0 years). For the whole population, LowExBP was associated with increased risk for fatal and non-fatal cardiovascular events and all-cause mortality (hazard ratio [HR]: 2.01, 95% confidence interval [CI]: 1.59-2.53, p < 0.001). In continuous analyses, a 10 mmHg decrease in exercise SBP was associated with higher risk (n = 9 HR: 1.13, 95% CI: 1.06-1.20, p < 0.001). LowExBP was associated with increased risk regardless of clinical presentation (coronary artery disease, heart failure, hypertrophic cardiomyopathy or peripheral artery disease), exercise mode (treadmill or bike), exercise intensity (moderate or maximal), or LowExBP category (all p < 0.05). However, bias toward positive results was apparent (Eggers test p < 0.001 and p = 0.009).

CONCLUSION

Our data show that irrespective of clinical or exercise conditions, LowExBP independently predicts fatal and non-fatal cardiovascular events and all-cause mortality.

Short-term risk after initial observation for chest pain

Few studies have evaluated the necessity of immediate stress testing after observation for chest pain. The purpose of this study was to assess the safety of outpatient stress testing after discharge from a chest pain unit. We hypothesized that discharge from a chest pain unit before stress testing is associated with a low rate of short-term adverse outcomes. This was a retrospective chart review of managed care patients discharged from the chest pain unit before the performance of stress testing. Records were reviewed for the occurrence of adverse cardiac outcomes before an outpatient stress test up to 60 days post-discharge. Primary outcomes were defined as death or myocardial infarction, and secondary outcomes as readmission for chest pain evaluation, unstable angina, or congestive heart failure. Three hundred forty-four patients were identified. One hundred sixty-six patients had either a recent prior stress test (17) or an outpatient test (149) performed within 60 days of discharge. During that time, 2 patients (0.6%) had a fatal out-of-hospital cardiac event, and there were 27 subsequent chest pain visits to the Emergency Department by 24 patients (7.0%). Nine patients (2.6%) were admitted to the hospital and 10 (2.9%) were readmitted to the observation unit for chest pain. We conclude that patients who have negative serial electrocardiograms and enzyme testing in a chest pain unit are at low risk for short-term cardiac events. Appropriately selected patients may be discharged for subsequent outpatient testing.

Risk stratification after acute myocardial infarction in the reperfusion era

Historically, risk stratification for survivors of acute myocardial infarction (AMI) has centered on 3 principles: assessment of left ventricular function, detection of residual myocardial ischemia, and estimation of the risk for sudden cardiac death. Although these factors still have important prognostic implications for these patients, our ability to predict adverse cardiac events has significantly improved over the last several years. Recent studies have identified powerful predictors of adverse cardiac events available from the patient history, physical examination, initial electrocardiogram, and blood testing early in the evaluation of patients with AMI. Numerous studies performed in patients receiving early reperfusion therapy with either thrombolysis or primary angioplasty have emphasized the importance of a patent infarct related artery for long-term survival. The predictive value of a variety of noninvasive and invasive tests to predict myocardial electrical instability have been under active investigation in patients receiving early reperfusion therapy. The current understanding of the clinically important predictors of clinical outcomes in survivors of AMI is reviewed in this article.

[The prognostic factors after an acute myocardial infarct treated with fibrinolytics]

BACKGROUND

The usefulness of the exercise test in evaluating patients with an acute myocardial infarction treated with fibrinolytics is controversial. On the other hand, the prognostic value of a patent infarct-related artery has not been clearly established. The objectives of this study were to assess the validity of the exercise test and to study the prognostic value of the artery patency after a myocardial infarction.

MATERIAL AND METHODS

We studied 99 patients with a myocardial infarction treated with fibrinolytics, non-complicated. An exercise test and a cardiac catheterization were performed in the first month. The patients were followed-up for 2 years, recording the major cardiac events (death and reinfarction) and the minor events (angina class (II, left cardiac failure class (II or maintained ventricular tachycardia).

RESULTS

On multivariate analysis with Cox regression, a workload < 4 METS at the exercise test was the only independent prognostic factor of major events (RR 5.6; CI 95% 1.68-19). The independent prognostic factors of minor events were: multivessel disease (RR 3.36; CI 95% 1.56-7.24), anterior infarction (RR 3.15; CI 95% 1.3-7.6), abnormal exercise test (RR 2.98; CI 95% 1.46-6.09) and ejection fraction < or = 40% (RR 2.48; CI 95% 1.07-5.74). The patency of the infarct-related artery was not a predictor of events.

CONCLUSIONS

The exercise test is useful in predicting the prognosis in patients treated with fibrinolytics. An occluded infarct-related artery was not an independent predictor of cardiac events in 2 years of follow-up.