Risk Stratification Post-MI With Preserved EF
Will an arrhythmic risk stratification protocol successfully identify patients with ejection fraction (EF) ≥40% post-myocardial infarction (MI) who might benefit from implantable cardioverter-defibrillator (ICD) due to high risk of ventricular arrhythmia?
The PRESERVE-EF (Risk Stratification in Patients With Preserved Ejection Fraction) study is a prospective observational study that enrolled patients from 7 cardiology departments in Greece. Patients were at least 40 days post-MI (and ≥90 days after coronary artery bypass graft surgery if applicable) with EF ≥40%, with no active ischemia, with or without revascularization, and on optimally tolerated medical treatment. Exclusion criteria included secondary prevention indication for ICD, prior pacemaker, and recent syncope or presyncope. Signal-averaged electrocardiogram (ECG) and 24-hour ambulatory ECG were performed to identify any of 7 noninvasive risk factors for sudden cardiac death (SCD):
- More than 30 premature ventricular contractions per hour
- Nonsustained ventricular tachycardia
- Late potentials
- Prolonged QTc
- Increased T-wave alternans
- Reduced heart rate variability
- Abnormal deceleration capacity with abnormal turbulence
Study participants with at least one noninvasive risk factors were offered programmed ventricular stimulation (PVS). Those who developed sustained monomorphic ventricular tachycardia, ventricular flutter, or polymorphic ventricular tachycardia with PVS were considered inducible and were offered ICD. The primary endpoint was defined as a major arrhythmic event (i.e., SCD, ventricular tachycardia, ventricular fibrillation, or ICD activation). The secondary endpoint was total mortality.
A total of 575 patients was enrolled from April 2014 to July 2018 and then followed for a mean duration of 32 months. At least 1 noninvasive risk factor was identified in 204 (35.5%). Of the 152 patients who consented to PVS, 41 (7.1%) were inducible. ICD was implanted in 37 but declined by 4. The primary endpoint occurred in 9 patients in the form of appropriate device therapy, at which point the steering committee recommended termination of the study for ethical reasons in light of an emerging high-risk population. No primary endpoint occurred in patients who had been non-inducible nor in whom no noninvasive risk factors were identified. Kaplan-Meier curves were constructed for the primary endpoint and the logrank test was applied, yielding a plogrank <0.001. The secondary endpoint occurred in 5 patients; 4 patients who were non-inducible had non-cardiac death and 1 patient who was inducible experienced a non-SCD death during an episode of acute renal failure (plogrank < 0.001). The authors indicate that the risk stratification approach had a sensitivity of 100%, specificity of 93.8%, positive predictive value of 22%, and negative predictive value of 100%.
A risk stratification protocol, which utilized 24-hour ambulatory ECG and signal-averaged ECG followed by PVS in selected patients, successfully identified post-MI patients with EF ≥40% at high risk of SCD who may benefit from ICD.
The 2017 American Heart Association, American College of Cardiology, and Heart Rhythm Society guideline for management of patients with ventricular arrhythmias and the prevention of SCD provides indications for primary prevention ICD in patients with ischemic heart disease. Current recommendations include only those with reduced EF or New York Heart Association Class IV heart failure. However, the guidelines include a value statement (Section 7.1.2) that states that an ICD provides high value in the primary prevention of SCD, particularly when the patient’s risk of death due to a ventricular arrhythmia is deemed high and the risk of nonarrhythmic death is deemed low based on the patient’s burden of comorbidities and functional status. The PRESERVE-EF risk stratification protocol might serve to identify such post-MI patients with EF ≥40% who are at high risk of ventricular arrhythmia for whom ICD may provide high value.
Keywords: Myocardial Infarction, Stroke Volume, Arrhythmias, Cardiac, Ventricular Fibrillation, Ventricular Flutter, Tachycardia, Ventricular, Syncope, Risk Factors, Death, Sudden, Cardiac, Defibrillators, Implantable, Electrocardiography, Electrocardiography, Ambulatory
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