Extensive inferior infarction with right ventricular and posterior wall extension

ECG 2A: Bradycardia with narrow QRS; atrial activity difficult to detect; possible regular atrial activity visible in V3 with 2:1 pattern (probable atrioventricular conduction disorder); Q-wave in the inferior territory and from V4 to V6; high amplitude R wave in V1 and V2 compatible with a posterior infarction; tall elevation (Pardee wave) of the ST-segment in the inferior leads with higher ST-segment amplitude in lead III than in lead II; reciprocal depression in lead I and aVL (large amplitude) and in V1-V2; moderate elevation in V4, V5, V6;

ECG 2B: Tracing recorded simultaneously with right-sided and posterior leads; the inferior elevation is associated with a significant elevation in the right leads (V3R, V4R) and in the posterior leads with Q-waves;

Comments: This patient underwent coronary angiography, which revealed a right proximal coronary thrombosis. Several electrocardiographic signs found in this patient point to a proximal right coronary artery disease: elevation greater in lead III than in lead II (suggestive of a right coronary involvement as opposed to the circumflex), deep depression in leads I, aVL, right ventricular extension with probable atrioventricular conduction disorder and posterior extension (suggestive of proximal rather than distal involvement). When there is involvement of both the right ventricle and the posterior wall of the left ventricle, electrocardiographic lesions may be masked due to the concomitant presence of vectors of opposite direction (elevation in V1 for right ventricular extension versus depression in V1 for a posterior wall disease).

As explained previously, defining the presence of right ventricular disease is clinically determinant. It is suspected in the presence of an inferior infarction with signs of right heart failure, hypotension, cardiogenic shock or during an episode of collapse following administration of  nitroglycerine. The presence of ST-segment elevation in the right-sided leads is a strong and independent predictive factor of major complications and hospital mortality. Intra-hospital mortality is considerably increased by cardiogenic shock, rhythm disturbances, conduction disturbances (up to 50% atrioventricular block or sinus node dysfunction) and mechanical complications (cardiac rupture, etc.). The observation of an increased incidence of atrial fibrillation can be explained by atrial infarction, acute atrial dilatation and increased loading conditions. It should also be noted that the inferior infarction with right ventricular extension configuration is associated with the highest risk of occurrence of severe ventricular rhythm disorders (sustained ventricular tachycardia or ventricular fibrillation), a risk much higher than for an isolated inferior infarction but also higher than for an anterior infarction.

The short-term prognosis is therefore unfavorable compared to that of an isolated inferior infarction, which is currently associated with limited mortality. Conversely, it appears that the long-term prognosis for survivors is no different than that for patients with isolated inferior infarction. Hemodynamic failure and arrhythmogenic risk in relation to right ventricular disease thus appear serious but reversible, emphasizing the importance of initial management, since the prognosis beyond the tenth day remains solely dependent on left ventricular function.

When confronted with a patient with biventricular infarction (inferior + right ventricle), acute-phase treatment includes

1. rapid reperfusion which allows a rapid recovery of right ventricular contractility; an incomplete or late reperfusion is associated with increased mortality;
2. adequate vascular filling is imperative to maintain adequate right ventricular ejection volume and proper left ventricular function; close monitoring of diuresis and arterial pressure is necessary in this setting;
3. intravenous nitroglycerine and diuretics are contraindicated because they decrease venous return, reduce right ventricular filling and left ventricular preload and promote hypotension; beta-blockers should be used with caution in view of the frequency of conduction disturbances;
4. ventricular pacing, usually temporary, is proposed in the presence of a conduction disorder; it may be desirable to implant 2 pacing leads (one in the atrium and one in the ventricle) in order to preserve atrioventricular synchronism and to optimize the hemodynamics of the patient;
5. prolonged surveillance in intensive care is essential due to the risk of sudden death from ventricular rhythm disorders;
6. inotropic drugs (dobutamine), intra-aortic counterpulsion and right ventricular assistance may be proposed in the most severe forms;

Take-home message: Risk of sudden death and conduction disorders is particularly elevated in patients with an inferior infarction with right ventricular extension even in the absence of severe left ventricular dysfunction. This risk is temporary, regresses after the acute phase but involves close initial monitoring.