Painful Left Bundle Branch Block Syndrome: A Puzzle in the Diagnosis of Chest Pain

Chest pain is one of the main reasons patients seek emergency care. Although myocardial infarction is an immediate concern, not all chest pain is caused by myocardial ischemia. A rarely diagnosed condition, painful left bundle branch block (LBBB) syndrome, poses a challenge for healthcare professionals because it mimics angina symptoms in the absence of coronary artery disease.

What Is Painful Left Bundle Branch Block Syndrome?

Painful LBBB syndrome is characterized by the simultaneous occurrence of chest pain and LBBB, usually triggered by an increase in heart rate, such as during physical exertion. Unlike classic angina, this condition is not related to myocardial ischemia; in other words, there is no evidence of coronary obstruction. Studies such as that by Shvilkin et al. observed that the electrocardiographic pattern of painful LBBB shows an inferior QRS axis and a low S-to-T wave ratio in the precordial leads, indicating a recent-onset rather than chronic LBBB.

Possible Mechanisms of Pain

The mechanism underlying pain in painful LBBB syndrome is believed to be the dyssynchronous ventricular contraction caused by LBBB. This dyssynchrony results in abnormal activation of the ventricular myocardium, in which the walls of the left ventricle are activated at different times, generating uneven stretch and tension in the muscle. This phenomenon is associated with prolonged isovolumic contraction and relaxation times, resulting in significant chest pain in some patients.

How to Diagnose Painful LBBB Syndrome?

Diagnosing painful LBBB syndrome is challenging and requires a high index of suspicion. During an exercise test, the abrupt appearance of LBBB together with chest pain, and the simultaneous disappearance of these findings at rest, are indicative of the syndrome. Tests such as coronary CT angiography and myocardial perfusion scintigraphy are essential to exclude myocardial ischemia. In this way, painful LBBB can be distinguished from classic angina pectoris and unnecessary invasive procedures can be avoided.

Treatment and Prognosis

Treatment options for painful LBBB syndrome are limited and usually focus on symptom control. Beta-blockers have been used successfully, as they lower the heart rate and prevent the triggering of painful LBBB. Patients who do not respond to medication may benefit from right ventricular or biventricular pacing, since these therapies help resynchronize ventricular contraction, eliminating the dyssynchrony responsible for the pain. Overall, the prognosis is favorable, and the condition tends to be self-limited, without progression to heart failure.

See Also

• Left Bundle Branch Block (LBBB)
• Revisiting the Strauss Criteria for the Diagnosis of Left Bundle Branch Block

Key Points

• Painful LBBB syndrome is a rare and frequently underdiagnosed condition characterized by chest pain occurring simultaneously with LBBB.
• The pain is caused by dyssynchrony of ventricular contraction, with no evidence of myocardial ischemia.
• The diagnosis is made by observing LBBB during exercise testing, together with exclusion of coronary artery disease.
• Treatments such as beta-blockers and pacing may help reduce symptoms.
• The prognosis is generally favorable, with a good response to appropriate treatment.