High-intensity Interval Training in Patients With Post-acute Coronary Syndrome

Inclusion Criteria: * Males or females aged ≥ 18 years * Acute coronary syndrome within 6 weeks (unstable angina, or non-ST elevation myocardial infarction (NSTEMI), or ST elevation myocardial infarction (STEMI with the presence of 2/3 criteria (i.e. typical chest pain, electrocardiographic ischemic change or elevated troponin T * Complete revascularization defined as no major epicardial coronary artery or bypass graft with a residual diameter stenosis \>50% and no residual left main stenosis ≥40% * Left ventricular ejection fraction \>40% * Stable doses of medication during the 4 weeks prior to enrolment (STEMI patients must be on a stable dose of beta-blocker) * Able to perform a maximal cardiopulmonary exercise test, 7) capacity and willingness to sign informed consent. Exclusion Criteria: * Recent coronary bypass surgery (\<6 months) * Incomplete revascularisation, left ventricular ejection fraction \<40% * Significant valvular disease (mitral stenosis, moderate to severe mitral insufficiency, aortic stenosis, or aortic insufficiency) * Uncontrolled hypertension (systolic blood pressure/diastolic blood pressure \>180/110 mmHg) * Significant resting electrocardiogram abnormalities (left bundle branch block, non-specific intraventricular conduction delay, left ventricular hypertrophy, resting ST-segment depression) * Chronic atrial fibrillation * Pacemaker or implantable cardioverter defibrillator * Low functional capacity (\<5 basal Metabolic Equivalent of Task \[METs\]) * Change of cardiac medications within 4 weeks of enrolment and any contraindication to exercise testing or exercise training.