Scenario: This is the beginning ECG strip (leads II and V1) from a 24-hour Holter study of a 72-year-old white man with congestive heart failure (CHF). The patient is asymptomatic and the Holter study is part of the patient’s routine cardiac care. What is your interpretation of his baseline rhythm?

Interpretation: One hundred percent biventricular (BiV) pacing at 77 beats per minute.

Given the rapid evolution of electrical device therapy, there are multiple pacemaker options to consider. The rhythm is regular, and a pacemaker spike can be appreciated preceding every QRS complex. Many patients with CHF have asynchronized ventricular contraction. This asynchrony diminishes ventricular filling time and compromises the cardiac output, which eventually leads to an increase in signs and symptoms of heart failure. Thus, resynchronization therapy with BiV pacing is designed to improve ventricular coordination. Biventricular...

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