Abstract Body (Do not enter title and authors here):
Description of Case:

An 81-year-old man with left bundle branch block (LBBB) and recent inguinal hernia repair presented with 2 weeks of dizziness and shortness of breath. On presentation, sinus tachycardia was noted with a heart rate of 100 bpm. While in the emergency department, he acutely developed complete heart block, initially with a right bundle branch block (RBBB) pattern escape at a rate of 53 bpm. Gradually, the escape slowed to 20 bpm with vomiting and hypotension so an emergent transvenous pacer was placed; he was paced at VVI 80 bpm with improvement in status. Transthoracic echocardiogram exhibited McConnell’s sign (Figure 1) with severe RV enlargement, severely reduced RV systolic function and normal LV systolic function. Arterial line tracings fluctuated with inspiration/expiration consistent with a pulsus paradoxus pattern (Figure 2) without evidence of pericardial effusion. CT angiography of the chest showed emboli in the bilateral main pulmonary arteries. For treatment, the patient was started on a therapeutic heparin drip, transitioned later to therapeutic apixaban. He did continue to require intermittent pacing and so underwent dual-chamber permanent pacemaker placement on hospital day 3.

Discussion:

EKG findings in patients with pulmonary emboli can be variable. In one prospective cohort study of 246 consecutive patients suspected to have pulmonary embolism (PE), only tachycardia (p = 0.008) and incomplete right bundle branch block (p = 0.002) amongst 28 total EKG findings evaluated were associated with confirmed pulmonary embolism by imaging. Interestingly, new RBBB may be a sensitive and specific marker for massive PE. In 50 patients with proven pulmonary embolism, all 16 cases with new RBBB on EKG were noted to have massive trunk obstruction (no patients with peripheral PEs had new RBBB). In the several case reports we found of patients with prior/observed LBBB and PEs who subsequently developed CHB, PEs were notably large, described as either bilateral or saddle-shaped, suggesting an association of acquired RBBB with significant PE burden. The cause of new complete heart block should always be acutely sought; in patients with baseline LBBB, a new RBBB leading to complete heart block can occur with massive/submassive PE. Rapid identification and treatment are needed to limit mortality in this often hemodynamically unstable entity.