Chronic Ischemic Arrhythmias

Article written and reviewed by Dr Luca Moretti

Chronic ischemic arrhythmias are rhythm disorders resulting from electrical alterations of the myocardium secondary to chronic ischemia.
They may manifest in patients with stable ischemic heart disease, a history of myocardial infarction, or left ventricular dysfunction, and are often associated with increased cardiovascular mortality.
Arterial hypertension, diabetes mellitus, and coronary atherosclerosis can contribute to myocardial electrical instability, increasing the risk of life-threatening ventricular arrhythmias.

The main pathophysiological mechanisms involved are:

• Chronic ischemia and myocardial fibrosis: Creation of reentry circuits due to areas of scar tissue.
• Autonomic nervous system dysfunction: Sympathetic overactivity with increased risk of ventricular arrhythmias.
• Action potential alterations: Changes in depolarization and repolarization favoring the onset of ectopic beats and tachycardias.

Classification of Ischemic Arrhythmias

Ischemic arrhythmias can be supraventricular or ventricular, with varying degrees of severity:

• Supraventricular arrhythmias: Atrial fibrillation, atrial flutter, atrial tachycardia.
• Ventricular arrhythmias: Ventricular extrasystoles, non-sustained and sustained ventricular tachycardia, ventricular fibrillation.

Clinical Features and Diagnosis

The clinical manifestations of ischemic arrhythmias vary according to the severity and type of arrhythmia. The main symptoms include:

• Palpitations.
• Dyspnea and exercise intolerance.
• Symptoms of heart failure in the case of persistent arrhythmias.
• Syncope or presyncope in sustained ventricular arrhythmias.

The most useful diagnostic tests include:

• Resting ECG: Shows signs of chronic ischemia, conduction abnormalities, and arrhythmias.
• 24–48 hour Holter ECG: Essential for identifying intermittent arrhythmias and correlating symptoms with arrhythmic episodes.
• Exercise testing: Useful to reveal ischemia-induced arrhythmias.
• Echocardiography: Assessment of ventricular function and detection of structural abnormalities.
• Cardiac magnetic resonance imaging: Identifies myocardial fibrosis and areas of ventricular dysfunction.
• Electrophysiological study: Indicated in high-risk patients to assess the arrhythmogenic substrate.

Treatment of Chronic Ischemic Arrhythmias

Treatment depends on the severity of the arrhythmia and the presence of symptoms.

Lifestyle modifications: Controlling cardiovascular risk factors, abstaining from alcohol and caffeine, and adequate management of heart failure reduce the incidence of arrhythmias.

Pharmacological therapy:

• Beta-blockers: Reduce cardiac automaticity and improve prognosis in ischemic patients.
• Class I and III antiarrhythmics: Indicated in selected patients, with attention to proarrhythmic effects.
• Anticoagulants: Necessary in patients with atrial fibrillation to prevent thromboembolic events.

Implantable devices:

• Implantable cardioverter-defibrillator (ICD): Indicated in patients at high risk of sudden death.
• Cardiac resynchronization therapy (CRT): Improves cardiac function in patients with ventricular dyssynchrony.

Catheter ablation: Indicated in patients with sustained ventricular arrhythmias or atrial fibrillation refractory to medical therapy.

Prognosis and Complications

Chronic ischemic arrhythmias are associated with an increased risk of sudden death, heart failure, and thromboembolism. Timely and targeted treatment is crucial to reduce mortality and improve quality of life.

References
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