Chronic Ischemic Arrhythmias

Chronic ischemic arrhythmias are rhythm disturbances caused by electrical changes in the myocardium secondary to chronic ischemia.

They may occur in patients with stable ischemic heart disease, post-myocardial infarction, or left ventricular dysfunction, and are often associated with an increased risk of cardiovascular mortality.
Hypertension, diabetes mellitus, and coronary atherosclerosis can contribute to the electrical instability of the myocardium, increasing the risk of dangerous ventricular arrhythmias.

The main pathophysiological mechanisms involved are:

• Chronic ischemia and myocardial fibrosis: Creation of reentry circuits due to scar tissue.
• Autonomic system dysfunction: Sympathetic overactivity with increased risk of ventricular arrhythmias.
• Action potential abnormalities: Modifications in depolarization and repolarization that favor the onset of extrasystoles 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 Presentation and Diagnosis

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

• Palpitations.
• Dyspnea and exercise intolerance.
• Signs of heart failure in cases of persistent arrhythmias.
• Syncope or presyncope in sustained ventricular arrhythmias.

The most useful diagnostic tests include:

• Baseline ECG: Shows signs of chronic ischemia, conduction abnormalities, and arrhythmias.
• 24-48 hours Holter ECG: Essential for identifying intermittent arrhythmias and correlating symptoms with arrhythmic episodes.
• Stress test: Useful for highlighting arrhythmias induced by ischemia.
• Echo-cardiography: Assessment of ventricular function and the presence of structural abnormalities.
• Cardiac MRI: Identifies myocardial fibrosis and areas of ventricular dysfunction.
• Electrophysiological study: Indicated for high-risk patients to assess the arrhythmic substrate.

Treatment of Chronic Ischemic Arrhythmias

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

Lifestyle modifications: Control of cardiovascular risk factors, avoidance of alcohol and caffeine, and proper management of heart failure reduce the incidence of arrhythmias.

Pharmacological therapy:

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

Implantable devices:

• Implantable cardioverter-defibrillator (ICD): Indicated in patients with a 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 essential to reduce mortality and improve quality of life.

Bibliography
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