Effect of Exercise Training on Left Ventricular Function in Patients Post Myocardial Infarction

Patients who have suffered a myocardial infarction are at significant risk for developing heart failure and progressive left ventricular dysfunction One of the proposed mechanisms responsible for this observation is reduction in myocardial beta-adrenergic receptor density due to elevated cell membrane protein G - protein coupled receptor kinase -2 (GRK2).

It is known that exercise training preserves heart function in patients who have suffered a myocardial infarction. The mechanism for this is not clear.

The purpose of this study is to examine the effect of exercise training on myocardial function and GRK2 levels in patients who have suffered a myocardial infarction, with the hypothesis that exercise training in this population reduces GRK2 levels and preserves or improves myocardial function.

Inclusion criteria

• Acute myocardial infarction
• Complete revascularization: no residual major epicardial coronary artery coronary stenosis ≥ 70%; no residual left main coronary stenosis ≥ 40%.
• Stage A-C heart failure, New York Heart Association class I-III.
• Stable dose of medications during the 4 weeks prior to enrolment.
• Able to perform a maximal cardiopulmonary stress test.
• Capacity and willingness to provide sign informed consent.

Exclusion criteria

• Pregnant
• Coronary artery bypass surgery: patients post coronary artery bypass graft exhibit wall motion abnormalities that may interfere with speckle tracking analysis.
• Incomplete revascularization with major epicardial coronary artery (left anterior descending, circumflex, or right coronary) stenosis ≥ 70%.
• Myocardial necrosis in the absence of significant flow limiting coronary artery stenosis or thrombosis, with the exception of documented STEMI and successful thrombolytic therapy resulting on no significant residual epicardial coronary artery stenosis.
• Significant valvular disease that is greater than moderate in severity
• History of non-ischemic cardiomyopathy (dilated, restrictive, infiltrative cardiomyopathy, hypertrophic, LV non compaction, or Takotsubo cardiomyopathy)
• Significant resting ECG abnormalities that preclude accurate speckle tracking.
• Paced rhythm.
• left bundle branch block
• Atrial arrhythmias (ex. persistent/permanent atrial fibrillation, atrial flutter).
• Frequent ventricular ectopics
• Significant ventricular arrhythmias (non-sustained ventricular tachycardia or syncope).
• New York Heart Association class IIIb - IV symptoms.
• Severe LV systolic dysfunction (Ejection fraction ≤ 30%)
• Active decompensated heart failure with orthopnea or paroxysmal nocturnal dyspnea.
• Uncontrolled resting arterial hypertension > 180/110 mmHg.
• More than moderate systemic disease
• Chronic inflammation or infection.
• Any contraindication to exercise training or any condition limiting ability to partake in adequate exercise stress testing or training (peripheral artery disease, articular, neurologic, or psychiatric pathology)