Chronic cor pulmonale

ECG: This tracing shows sinus rhythm, right atrial enlargement (voltage > 2.5 mm in lead II), negative P-wave in aVL, peaked and positive  P-wave in V1, normal PR interval, narrow QRS, R/S ratio = 1 in V1, R/S ratio < 1 from V2 to V6, extreme right axis deviation (258°);

Comments: Pulmonary hypertension and chronic cor pulmonale are common complications in patients with COPD in chronic respiratory failure. Chronic cor pulmonale is defined by hypertrophy and/or dilatation of the right ventricle due to pulmonary hypertension resulting from chronic respiratory or pulmonary circulatory disorders. The main causes of chronic cor pulmonale are chronic bronchitis, emphysema, severe pulmonary embolism, certain systemic diseases (lupus, scleroderma), primary pulmonary hypertension, kyphoscoliosis or morbid obesity.

It is difficult to differentiate electrical abnormalities related to the causal lung disease from those related to its cardiac consequences. We have previously seen that pulmonary emphysema in itself is able to generate electrocardiographic modifications without necessarily affecting the hemodynamics of the right heart. There is thus a wide variety of electrocardiographic findings depending on the causal disease and the predominance of one of these two factors.

The electrocardiogram can highlight:

1. Right atrial enlargement which is inconsistent in moderate forms, quasi-constant in severe forms; the P-waves are upright with, as in this patient, an increase in voltage in lead II, a positive and peaked P-wave in V1, negative in aVL;
2. The QRS-complexes frequently present abnormalities that can be related to the causal lung disease (emphysema) and/or the right ventricular hypertrophy; QRS duration is typically normal, the hypertrophy not being sufficient to cause a prolongation of the QRS; the onset of a complete right bundle branch block (QRS > 120 ms) is rare, whereas an incomplete block pattern is much more common; the QRS axis may be normal or deviated to the right; when emphysema is predominant (COPD patients), the QRS voltages are small or even greatly reduced; there is therefore no increase in R wave amplitude in V1 and V2 found in the other forms of right ventricular hypertrophy; conversely, in patients without emphysema (post-embolic PAH, for example), the typical pattern of right ventricular hypertrophy with dominant R wave and delayed intrinsicoid deflection in V1 can be found; it is common to observe large S waves in the left precordial leads with an R/S ratio < 1 in V6;
3. Non-specific repolarization abnormalities can be observed in conjunction with right ventricular hypertrophy;

Take-home message: In patients with chronic pulmonary heart disease complicating chronic respiratory disease, it is difficult to distinguish electrical alterations in relation to causal lung disease from those associated with cardiac impairment, particularly in the case of pulmonary emphysema.