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Electrocardiography (ECG) in Pulmonary Disorders
Electrocardiography is a useful adjunct to other pulmonary tests because it provides information about the right side of the heart (see Electrocardiography (ECG)) and therefore pulmonary disorders such as chronic pulmonary hypertension and pulmonary embolism.
Chronic pulmonary hypertension leading to chronic right atrial and ventricular hypertrophy and dilation may manifest as prominent P waves (P pulmonale) and ST-segment depression in leads II, III, and aVF; rightward shift in QRS axis; inferior shift of the P wave vector; and decreased progression of R waves in precordial leads.
COPD patients commonly have low voltage due to interposition of hyperexpanded lungs between the heart and ECG electrodes.
Pulmonary embolism (submassive or massive) may cause acute right ventricle overload or failure, which manifests classically (but not commonly) as right axis deviation (R > S in V 1 ), with S-wave deepening in lead I, Q-wave deepening in lead III, and ST-segment elevation and T-wave inversion in lead III and the precordial leads (S 1 Q 3 T 3 pattern). Right bundle branch block also sometimes occurs.
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