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recurrent syncope is known as one of the risk factors of sudden cardiac death.1 ) to give proper management and prevent sudden cardiac death , it is important to know the mechanism causing loss of consciousness in patients with hcmp . among various etiologies ,
bradyarrhythmia such as atrioventricular ( av ) conduction disturbance , a relatively rare complication associated with hcmp , also can make patient suffer from syncope or presyncope .
a 30-year - old female was referred to the cardiology center due to recurrent syncope episodes and aggravated shortness of breath for a month .
she was diagnosed as hcmp 7 years ago , and had been taken atenolol irregularly since then .
after experienced recurrent syncope episodes , she visited another medical center for evaluation of loss of consciousness .
cardiac evaluation , including conventional echocardiography and 24-hour ambulatory electrocardiogram ( ecg ) monitoring , could n't reveal the cause of repeated syncope .
the neurologic exams for differential diagnosis showed no evidence of seizure disorder or any other diseases , inducing loss of consciousness .
however , despite medication , symptoms developed more frequently , combined with shortness of breath and exercise intolerance . in 2012 , she visited our cardiology clinic for further evaluation and management of worsening symptoms under medical treatment .
initial ecg showed 2 : 1 av block with 36 beats / min of the ventricular rate ( fig .
the baseline two - dimensional echocardiography showed hcmp with asymmetric septal hypertrophy ( septal wall thickness during diastole 16 mm ) and systolic anterior motion of mitral valve ( fig .
to evaluate the cause of recurrent syncope , additional studies including stress echocardiography , 24-hour ambulatory ecg and treadmill test were performed . during
the stress echocardiography with bicycle exercise , when reached 50 watts of workload stage , mitral inflow pattern showed multiple spikes during a late filling phase by atrial contraction accompanied with high grade av block on ecg monitoring ( fig .
the baseline blood pressure was 91/59 mmhg ( systole / diastole blood pressure ) and 46 beats / min of the heart rate , but there was no hypotensive response representing dynamic left ventricular outflow tract obstruction .
simultaneous 24-hour ecg also showed conduction disturbance ( including 3 : 1 and 4 : 1 av block ) during the exercise and additionally disclosed 1 episode of non - sustained ventricular tachycardia ( nsvt ) ( fig .
subsequent treadmill test also revealed high grade av block with dyspnea and exhaustion at 7.0 mets of exercise under bruce protocol ( fig .
although there was no syncope event when ecg monitoring records high grade av block or nsvt in both 24-hour ecg and stress test , we thought this conduction disturbance and arrhythmia could play a role in repeated loss of consciousness and exercise intolerance . according to the guideline for risk stratification of sudden cardiac death in hcmp , based on her unexplained syncope episodes , it is reasonable to treat this patient with implantable cardioverter / defibrillator ( icd).2 ) patient underwent elective icd with dual - chamber pacemaker implantation
after that , patient showed no more conduction disturbance at high stage of workload and improved exercise capacity of 12.8 mets under bruce protocol without any distress in repeated stress test ( fig .
among the patients with hcmp , about 25 - 30% of patients experience symptoms of fainting , dizziness or impaired consciousness.2)3 ) a history of recurrent syncope episodes is one of the predictable risk factors for sudden cardiac death in younger patients.4 - 6 ) syncope in hcmp can be explained by two underlying mechanisms : hemodynamic mechanism and arrhythmic complications . among the arrhythmic causes for syncope ,
paroxysmal atrial fibrillation is the most common cause that induces loss of consciousness.7)8 ) unlike premature ventricular complex or nsvt , which is usually not associated with syncope,9 ) sustained ventricular tachycardia can be the cause of syncope and even sudden cardiac death in hcmp.10 ) however , besides these tachyarrhymia , bradyarrhythmia such as av conduction disturbance also cause syncope or pre - syncope in hcmp.11 ) there are only a very few case reports of hcmp combined with av block causing syncope both in pediatric and adult patients.12 - 16 ) despite repeated evaluation , including 24-hour ecg monitoring , conventional two - dimensional echocardiography , and invasive electrophysiological study , probable mechanism causing syncope can be identified only in a limited number of cases.11 ) however , it is important to understand the cause of syncope in hcmp to avoid risk of sudden cardiac death and to give proper management for each different condition .
medications , such as beta - blocker or calcium channel blocker , usual management for hcmp according to the guideline,2 ) might aggravate symptoms of patients with conduction disturbance .
stress echocardiography can be helpful to evaluate the cause of syncope in hcmp patients , which provoke exercise - induced hemodynamic change or any arrhythmic complication , either tachyarrhythmia or bradyarrhythmia causing various symptoms.11 ) this case describes repeated syncope episodes and exercise intolerance caused by conduction disturbance during exercise in hcmp patients .
rarely complicated in hcmp , physicians should keep in mind the probability of conduction disorder as a cause of syncope .
a 30-year - old female patient with known hypertrophic cardiomyopathy ( hcmp ) was admitted for recurrent syncope episodes . 
 electrocardiogram ( ecg ) showed 2 : 1 atrioventricular ( av ) block . 
 stress echocardiography with bicycle showed high grade av block at high stage of the exercise associated with exercise intolerance and dyspnea . 
 twenty - four hour ecg monitoring also revealed high grade av block and 1 episode of non - sustained ventricular tachycardia . 
 implantable cardioverter / defibrillator - pacemaker ( icd - p ) was inserted . 
 after implantation of icd - p , conduction disturbance and exercise intolerance were improved . 
 av block is a rare complication hcmp . 
 there are just a few case reports that present symptoms caused by conduction disturbance in hcmp . 
 this case describes repeated syncope episodes and exercise intolerance caused by conduction disturbance during exercise in hcmp patient . for evaluating the cause of syncope in hcmp 
 , stress echocardiography can be helpful to understand the probable mechanism of syncope .