Prognosis and risk stratification after myocardial infarction

Area of Science:

• Cardiology
• Electrophysiology
• Prognostics

Background:

• Left ventricular dysfunction is a primary determinant of prognosis post-myocardial infarction.
• Assessing risk involves ejection fraction, Holter monitoring, signal-averaged ECG, programmed ventricular stimulation, and heart rate variability.
• The presence of an 'arrhythmogenic substrate' can be detected by specific electrophysiological markers.

Purpose of the Study:

• To evaluate various methods for assessing prognosis after myocardial infarction.
• To determine the effectiveness of new techniques in identifying patients at risk of ventricular tachyarrhythmias.
• To compare the sensitivity and specificity of different risk assessment tools.

Main Methods:

• Signal-averaged electrocardiography (ECG) for detecting ventricular late potentials.
• Programmed ventricular stimulation to assess inducibility of ventricular tachyarrhythmias.
• Analysis of heart rate variability as an index of sympatho-vagal interaction.
• Estimation of ejection fraction and left ventricular end-systolic volume.
• Assessment of infarct-related artery patency and thrombolytic therapy effects.
• Consideration of neurological factors like depression.

Main Results:

• Left ventricular end-systolic volume may be a better predictor than ejection fraction.
• Signal-averaged ECG and programmed ventricular stimulation show sensitivity for predicting sustained ventricular tachycardia but are less sensitive for sudden death.
• Abnormal results in signal-averaged ECG or programmed stimulation increase arrhythmic event risk, but false-positive rates are high.
• Decreased heart rate variability is associated with poorer prognosis.
• Successful thrombolysis may reduce late potentials and prevent an abnormal electrophysiological milieu.
• Depression is an independent risk factor for mortality post-myocardial infarction.

Conclusions:

• New techniques like signal-averaged ECG and programmed stimulation show promise for identifying patients at risk of ventricular tachyarrhythmias, potentially surpassing conventional methods.
• Combining arrhythmogenic substrate assessment with left ventricular function parameters is suggested.
• High false-positive rates limit the individual applicability of current risk assessment methods.