An echocardiogram was performed and revealed no structural abnormalities other than a small patent foramen ovale (PFO). The test was stopped due to limiting chest discomfort that persisted until her heart rate returned to 100 bpm at 2 : 30 min of recovery and normal conduction was restored. She was able to exercise through her discomfort, reaching a peak heart rate of 171 bpm and 10.4 metabolic equivalent (MET) at 9 : 11 min of exercise. During the aberrant conduction and at peak exercise, her symptoms of chest pain and palpitations returned. She was referred for exercise stress testing using the Bruce protocol during which she developed a left bundle branch block (LBBB) with a QRS duration of 120 msec at a heart rate of 112 beats per minute (bpm) (Figure 2). Laboratory tests including hemoglobin and cardiac troponin T were normal.īaseline electrocardiogram demonstrating normal baseline conduction. 12-lead electrocardiogram was normal with the following intervals: PR interval was 154 millisecond (msec), QRS was narrow at 82 msec, and QT interval was normal at 392 msec, corrected QT (QTc) using Bazett’s formula was 431 msec (Figure 1). She had a normal physical exam and her only medication was an oral contraceptive. The patient was a 42-year-old woman who presented with exertional chest pain, palpitations, and dyspnea that resolved with rest. While this treatment has been used previously, our case has a longer followup than previously reported and demonstrates that the treatment is not durable in the absence of continued exercise. We describe a case associated with normal coronary arteries which was successfully treated with exercise training. The best treatment of this condition and its association with coronary disease remain unclear. It may lead to delays in proper management of those heart conditions.Exercise induced bundle branch block is a rare observation in exercise testing, accounting for 0.5 percent of exercise tests. A slowed heart rate may lead to fainting, irregular heart rhythms and other serious complications.īecause bundle branch block affects the electrical activity of the heart, it can sometimes complicate the accurate diagnosis of other heart conditions, especially heart attacks. The lack of signaling can slow the heart rate. If both the right and the left bundles are blocked, the main complication is a complete blockage of the electric signaling from the upper to the lower chambers of the heart. Having high blood pressure or heart disease increases the risk of having bundle branch block. Bundle branch block is more common in older adults than in younger people. Risk factors for bundle branch block include: High blood pressure in the pulmonary arteries (pulmonary hypertension).Heart structure problems that are present at birth (congenital heart defects) - such as a hole in the wall separating the upper chambers of the heart (atrial septal defect).Blood clot in the lungs (pulmonary embolism).Thickened, stiffened or weakened heart muscle (cardiomyopathy).Inflammation of the heart muscle (myocarditis).Sometimes, there is no known cause.Ĭauses can include: Left bundle branch block The cause for bundle branch blocks can differ depending on whether the left or the right bundle branch is affected. As a result, the heart beats irregularly. If one or both of these branch bundles are damaged - due to a heart attack, for example - the electrical impulses can become blocked. These impulses travel along a pathway, including two branches called the right and the left bundles. CausesĮlectrical impulses within the heart muscle cause it to beat (contract). If you have heart disease or have been diagnosed with bundle branch block, ask your provider how often you should have follow-up visits. If you've fainted, see a health care provider to rule out serious causes. Rarely, symptoms of bundle branch block may include fainting (syncope) or feeling as if you're going to faint (presyncope). Some people with the condition don't know they have bundle branch block. In most people, bundle branch block doesn't cause symptoms. When it does, treatment involves managing the underlying health condition, such as heart disease, that caused bundle branch block. Bundle branch block might not need treatment.
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