Article, Cardiology

Hypertrophic cardiomyopathy: electrocardiographic manifestations and other important considerations for the emergency physician

Diagnostics

Hypertrophic cardiomyopathy: electrocardiographic manifestations and other important considerations for the emergency physician

Brian S. Kelly MDa, Amal Mattu MDb, William J. Brady MDc,*

aDepartment of Emergency Medicine, Mount Carmel Health System, Columbus, OH 43123, USA

bDepartment of Emergency Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA

cDepartment of Emergency Medicine, University of Virginia, Charlottesville, VA 22911, USA

Received 16 April 2006; accepted 17 April 2006

Abstract hypertrophic cardiomyopathy is one of the most common inherited primary cardiac disorders and the most common cause of sudden cardiac death in young athletes. With advances in technology, it is now recognized that HCM affects individuals of all ages. Many patients with HCM will have a benign course with few symptoms. Some patients, however, possess risk factors that greatly increase the likelihood of sudden death if their disease remains undiagnosed. Therefore, it is imperative that emergency physicians be familiar with the symptoms and typical electrocardiogram manifestations of HCM. Three illustrative cases are presented with a review of the disease.

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Introduction

In the mid-19th century, French pathologists first described the pathology of a cardiac disorder known today as hypertrophic cardiomyopathy (HCM). Because, in part, of the heterogeneity of this disease as well as technological advances in genetic testing, HCM has become the preferred name, replacing previous names such as hypertrophic obstructive cardiomyopathy and idiopathic hypertrophic subaortic stenosis, which described the typical, but not universal, features of left ventricular outflow tract (LVOT) obstruction and the predilection for asymmetrical hypertro- phy of the ventricular septum. Hypertrophic cardiomyopa-

* Corresponding author.

E-mail addresses: [email protected] (A. Mattu)8 [email protected] (W.J. Brady).

thy accurately reflects the primary diagnostic feature of a thickened myocardium without ventricular dilation in absence of conditions known to secondarily result in ventricular hypertrophy (eg, systemic hypertension and aortic stenosis).

Over the last 50 years, scientific interest has led to increased understanding of this extremely variable disease. Hypertrophic cardiomyopathy is currently recognized to be one of the most common inheritED diseases of the heart, occurring in as many as 1 in 500 individuals [1-4]. Early studies suggested annual mortality rates as high as 3% to 6% due largely to Sudden Cardiac Death in patients with HCM [1,3,4]. These early studies were primarily conducted at tertiary referral centers and included patients preferen- tially referred because of the severity of their symptoms [4]. The annual mortality of Unselected populations with HCM is estimated to be 1% to 2% [1,3,4].

0735-6757/$ – see front matter D 2007 doi:10.1016/j.ajem.2006.04.017

case presentations”>Case presentations

Case 1

A 30-year-old man presented to the emergency depart- ment (ED) after an episode of severe lightheadedness and palpitations that began while he was running to catch a bus. The symptoms persisted for 20 minutes despite resting, then resolved without any interventions. The patient had no medical history or history of drug use, no family history of early Cardiac conditions, and no prior similar episodes. Upon arrival to the ED, he was completely asymptomatic. His vital signs and physical examination results, including the cardiac examination results, were normal. An electro- cardiogram (ECG) was obtained (Fig. 1) and interpreted by the emergency physician as bLVH, otherwise normal.Q The cardiology interpretation was bNormal sinus rhythm, left ventricular hypertrophy, lateral infarct age undetermined.Q No previous ECGs were available for comparison.

Laboratory studies including one set of cardiac markers were ordered on the patient and were all normal. A chest radiograph was also obtained and demonstrated a normal heart size and no abnormalities. The patient demonstrated no dysrhythmias while being monitored in the ED. He was then discharged, still asymptomatic, with instructions for outpatient follow-up. Two days later, the patient collapsed while once again running to catch a bus. Paramedics were called immediately. When they arrived the patient was unconscious, pulseless, and apneic. His cardiac rhythm was ventricular fibrillation (Fig. 2). Standard advanced life support measures used by the paramedics and subsequently by ED staff were unsuccessful and the patient died. At autopsy, significant hypertrophy of the ventricular septum was noted. There was no evidence of a prior myocardial infarction, nor was there evidence of coronary atheroscle-

rotic disease or systemic drug toxicity. The presumed cause of death was HCM.

Case 2

A 25-year-old man presented to the ED complaining of severe palpitations and severe lightheadedness with near- syncope while playing basketball. The symptoms lasted for only 5 to 10 minutes before resolving with rest. The patient denied any medical history, family history of medical illness, drug use, or prior similar episodes. Upon arrival to the ED, he was asymptomatic. His vital signs and his physical examination were normal. An ECG was obtained (Fig. 2) and interpreted by both an emergency physician and a cardiologist as notable for left ventricular hypertrophy (LVH) and evidence of a prior lateral myocardial infarction. No previous ECGs were available for comparison (Fig. 3). The patient was admitted to the hospital for further evaluation of the episode of near-syncope and the Abnormal ECG. All laboratory studies, including serial cardiac enzymes, were normal. The chest radiograph was normal as well. Twenty-four hours of cardiac monitoring failed to reveal any dysrhythmias. The patient was then referred for a Doppler echocardiogram. There was no evidence of Wall motion abnormality that would normally be expected with a prior myocardial infarction, and the patient’s ejection fraction was normal. However, the study did reveal ventricular septal hypertrophy with some LVOT obstruction, diagnostic of HCM. The patient was then prescribed b-blocker medications and discharged for outpatient fol-

low-up with a cardiologist.

Case 3

A 29-year-old man presented to the ED complaining of palpitations and lightheadedness during Sexual activity. The

Fig. 1 (Case 1) Normal sinus rhythm with large-amplitude QRS complexes consistent with LVH and nonspecific T-wave abnormality. Deep narrow Q waves are also present in the lateral leads I, aVL, V5, and V6.

Fig. 2 (Case 1) Ventricular fibrillation.

symptoms persisted for 10 to 15 minutes before resolving without any intervention. The patient reported that he had presented to the ED on 2 prior occasions in the past month for similar complaints: on the First visit, he experience a near-syncopal episode while mowing the lawn, and on the second visit he experienced a syncopal episode while watching television. Both of those episodes were preceded by palpitations. He was discharged from the ED after the first visit after having an ECG and normal laboratory studies. He was admitted to the ED observation unit during the second presentation, whereupon he underwent serial cardiac enzyme testing and cardiac monitoring. He was discharged after the negative workup and instructed to follow up with a primary care physician, but he had not yet done so. The patient denied any medical history, family history of early cardiac disease, or drug use.

On the current visit, the patient remained asymptomatic at the time of ED arrival. His vital signs and physical examination, including cardiac examination, were normal. An ECG was obtained (Fig. 4). The ECG was interpreted by the emergency physician as being highly suggestive of HCM. Of note, there was no significant difference in the ECG when it was compared with the ECGs from the patient’s 2 prior visits. Each of the past ECGs had been interpreted (by separate cardiologists) as bNormal sinus rhythm, left ventricular hypertrophy, lateral myocardial infarction of indeterminate age.Q The emergency physician

referred the patient for immediate Doppler echocardiogra- phy, which confirmed the diagnosis of HCM. The patient was then admitted to the cardiology service and has been managed well on b-blocker medications.

Discussion

Pathophysiology

The heterogeneity of HCM can largely be explained through examination of the genetic mutations responsible for disease production. Hypertrophic cardiomyopathy is known to result from variable penetrance of the mendelian dominant inheritance of mutations in genes that encode proteins of the cardiac sarcomere. Laboratory studies have implicated more than 150 different mutations in multiple sarcomeric proteins with most the mutations occurring in the following proteins: including b myosin heavy chain (~35%), troponin T (~15%), myosin-binding protein C (~15%), and a-tropomyosin (b5%) [1,2,4]. Recently, mutations of genes coding for mitochondrial enzymes have been linked to the HCM phenotype [5]. Studies performed on pedigrees of different genotypes have led to the discovery that some mutations carry a benign prognosis, whereas other mutations result in early phenotypic disease expression and worse prognosis.

Fig. 3 (Case 2) Normal sinus rhythm with LVH and deep narrow Q waves in the lateral leads I, aVL, V5, and V6.

Fig. 4 (Case 3) Normal sinus rhythm with LVH and deep narrow Q waves in the lateral leads I and aVL.

Phenotypic manifestation of HCM is complicated further by factors such as modifier genes or environmental influences [2]. These complexities result in the different phenotypic manifestations of HCM even within families with the same genetic defect [3]. It therefore comes as no surprise that the clinical presentation and disease course is highly variable.

These genetic mutations result in LVH, which cannot be attributed to other commonly known etiologies. The magnitude of hypertrophy is highly variable ranging from mild (13-15 mm) to severe (N30 mm) [2]. The distribution of hypertrophy is also variable, but is most often asymmetric and most pronounced in the anterior ventricular septum [2]. Other patterns of hypertrophy associated with HCM include symmetric or concentric LVH (~20%) and apical (~10%). Spontaneous increase in ventricular hypertrophy is common during periods of rapid growth and is most apparent in adolescence. Upon completion of adolescence, the magni- tude of hypertrophy often remains stable throughout Adult life but may paradoxically decrease.

Postmortem histologic examination of myocardial sam- ples in HCM reveals loss of the normal parallel myocyte architecture, a condition known as myocyte disarray. Other findings include myocardial fibrosis, coronary artery abnor- malities including increased collagen deposition in the vessel walls, and narrowing of the arteriolar lumen. The features may serve as the substrate for arrhythmias in HCM. Other abnormalities associated with HCM include malformations of the mitral valve leaflets and severe systolic anterior motion (SAM) of the mitral valve. These abnormalities can lead to abnormal leaflet coaptation, mitral

regurgitation, and additional LVOT obstruction.

Clinical presentation

Family history is particularly important in patients with suspected HCM. A history of early-onset cardiac disease or,

especially, sudden cardiac death in a young relative increases the likelihood of HCM. In addition, because of autosomal dominant inheritance, a family history of HCM greatly increases the risk for HCM.

Patients with HCM may be completely asymptomatic, but will usually present with complaints related to LVOT obstruction and diastolic dysfunction. Symptoms are nonspecific and include dyspnea, exercise intolerance, dizziness, and near syncope or syncope. The severity of these symptoms may change throughout the day. Because of the dynamic nature of the degree of obstruction in HCM, patients may be asymptomatic at rest, but may become symptomatic even with minimal exertion. In addition, symptoms may worsen after large meals or alcohol ingestion [3].

Chest pain is more common in younger patients and may signal cardiac ischemia secondary to a mismatch in oxygen Supply and demand to the thickened ventricle. In severe hypertrophy, filling of the coronary arteries during diastole may become compromised. In addition, coronary arteriolar narrowing may limit blood flow reserve during periods of increased oxygen demand.

It is particularly important to inquire about near syncope or syncope in patients with suspected HCM. Lightheaded- ness and syncope occur commonly in patients with HCM and may be related to decreases in blood pressure due to LVOT obstruction. Alternatively, syncope should alert the clinician to the possibility of episodic atrial or ventricular arrhythmias, especially when it occurs in association with palpitations [3]. It is believed that children who present with syncope secondary to suspected HCM represent a particularly high-risk group and should receive aggressive initial evaluation.

Unfortunately, SCD may be the initial and only manifestation of disease, with the diagnosis of HCM made at postmortem examination after the death of a previously

Fig. 5 Normal sinus rhythm with LVH and deep narrow Q waves in the lateral leads V5 and V6.

healthy individual [1,2,5,6]. Despite increased awareness, HCM remains one of the most common causes for sudden death in young athletes.

Physical examination is more likely to be abnormal in patients with LVOT obstruction. Palpation of the carotid artery may reveal an initial brisk upstroke with subsequent collapse and secondary rise in late systole because of dynamic LVOT obstruction. Examination of the precordium may reveal a nondisplaced, hyperdynamic point of maximal impulse or a double apical impulse during systole as the hypertrophied noncompliant left ventricle contracts force- fully. Less commonly, a triple apical impulse may occur secondary to the addition of a palpable atrial gallop. An S4 gallop may be heard during atrial systole.

The classic description of the cardiac murmur in HCM referred to patients with subaortic obstruction only and may be present in as few as 30% to 40% of patients [7]. In these patients, auscultation may reveal a harsh crescendo- decrescendo systolic ejection murmur, which is best appreciated at the apex and radiates to the sternal notch. The intensity of the murmur is increased by maneuvers that decrease preload such as standing, Valsalva maneuver, or amyl nitrite administration. The murmur of HCM is unique from nearly all other cardiac murmurs in that it increases with Valsalva, making the performance of this maneuver very important during cardiac examination. In patients with concurrent mitral valve abnormalities, a holosystolic murmur that radiates to the axilla may be appreciated, reflecting Mitral regurgitation.

Diagnosis

Once the diagnosis of HCM is considered, the workup should generally include a chest x-ray, an ECG, and a transthoracic echocardiogram with Doppler examination. Of these examinations, the ECG and echocardiogram have the highest yield, as the chest x-ray will likely be normal, but

may be helpful for ruling out other conditions. Unlike many other forms of cardiomyopathy, HCM generally is associ- ated with a normal heart size on chest x-ray because the hypertrophy is primarily limited to the septum. Because of the complex, time-consuming, and cost-prohibitive nature of genetic testing, its use is limited to investigational research and is not available for routine clinical practice [2].

Most patients with HCM will have an abnormal ECG [1,8,9]. It is important to note that the ECG may be abnormal even when echocardiography fails to demonstrate hypertro- phy [3,8,10]. The ECG findings present in patients with HCM depend on the pattern and extent of myocardial hypertrophy. Characteristic findings of LVH are common and include high-voltage R waves in the anterolateral leads (V4, V5, V6, I, and aVL) [3,6,9,11]. Prominent R waves may be present in leads V1 and V2 as well [12]. The most frequent abnormalities found are large-amplitude QRS complexes consistent with LVH and associated ST-segment and T-wave changes [1,13]. Deep, narrow Q waves are common in the inferior (II, III, aVF) and lateral (I, aVL, V5, and V6) leads in patients with septal hypertrophy and may mimic myocardial infarction [3,6,9,11]. The morphology of the Q waves–deep and very narrow–is perhaps the most characteristic and specific finding of HCM. Although often these Q waves are mistaken for those of myocardial infarction, it should be recognized that infarction-related Q waves are wider, at least

0.04 seconds (ie, at least 1 mm wide on Standard ECG paper). The Q waves of HCM are rarely this wide. In the authors’ experience, deep narrow Q waves in the lateral leads are much more common than in the inferior leads. These Q waves may appear in all of the lateral leads–I, aVL, V5, and V6 (Fig. 1); they may predominate in just leads I and aVL (Fig. 4); or they may predominate in just leads V5 and V6 (Fig. 5). Although large-amplitude QRS complexes are the most common finding in HCM, deep narrow Q waves in the lateral leads are the most specific finding and should

management options“>Fig. 6 apical hypertrophic cardiomyopathy. Normal sinus rhythm with LVH and deeply inverted T waves in the mid and lateral precordial leads. T wave abnormality is also present in the inferior leads in this patient.

immediately prompt a high degree of suspicion when they are found. A less common variant of HCM involves isolated apical hypertrophy. Patients with apical HCM will frequently have deeply inverted T waves in the mid and lateral precordial leads (Fig. 6) [1,3,6,9].

Shimizu et al examined the chronological ECG changes in carriers with the deletion of lysine 183 (Lys183del) in the Cardiac troponin I gene compared with noncarriers and found Abnormal Q waves in leads I, II, III, aVF, V5, and V6 were frequently observed during the early teenage years. In contrast, carriers of the Lys183del in cTnI older than 20 years were more likely to demonstrate abnormal Q waves primarily in I, aVL, and other lateral leads. They concluded that sensitivity, specificity, positive predictive value, and negative predictive value of abnormal Q waves in the teens of their study population was 67%, 100%, 100%, and 78%,

respectively [13].

The transthoracic echocardiogram is one of the most useful tests in patients with HCM. It can document a number of findings including the degree of hypertrophy, systolic or diastolic dysfunction, the presence of LVOT or mid-ventricular obstruction, and mitral valve abnormalities including the degree of SAM. Most patients with HCM have varying degrees of diastolic dysfunction. Systolic dysfunc- tion is rare in the early course of the disease, but as the disease progresses to generalized dilated cardiomyopathy over the course of many years, systolic dysfunction becomes common as well. The direction and degree of mitral regurgitation, if present, can also be documented. The addition of Doppler studies is important to correctly identify outflow obstruction and mitral regurgitation. Patients without obstruction at rest should undergo repeat Doppler

echocardiogram examination after appropriate provocation to evaluate for latent obstruction [3].

Sudden cardiac death

Sudden cardiac death is the most feared complication of HCM. It is an evolving topic of intense investigation. Several clinically useful risk factors have been identified. The predictive value of each factor is low; thus, a collective risk profile, created by accurate assessment of individual risk factors, is the best method to identify high-risk patients [5]. Individual risk factors for SCD include prior cardiac arrest, episodes of sustained ventricular tachycardia, recur- rent syncope, especially when associated with exertion, a family history of 1 or more SCDs, extreme LVH (maximum wall thickness N30-35 mm), the presence of LVOT gradient N30 mm Hg, an abnormal blood pressure response during exercise, and the presence of nonsustained ventricular tachycardia during ambulatory ECG monitoring [2,4,5,14].

Collectively, a risk profile with 2 or more individual risk factors suggests a high annual risk of SCD.

The risk profile can be used to guide therapy. In patients with zero or one risk factor, the annual SCD rate is approximately 1%. This group represents most patients with HCM. In patients with 2 or more risk factors, the annual incidence of SCD is significant and prophylactic therapy with automatic implantable cardioverter/defibrillator (AICD) or amiodarone is warranted [1,4,5].

Management options

Hypertrophic cardiomyopathy remains the most common cause of sudden death during athletic endeavors [2,4]. It is

therefore extremely important to recommend that any patient suspected of having HCM avoid all intense, competitive, or isometric activity. In general, light aerobic exercise such as walking or noncompetitive swimming, is considered safe [1].

Treatment strategies aim to improve or relieve the symptoms caused by LVOT obstruction or abnormal ventricular function due to diastolic dysfunction. Tradition- ally, b-blocker medications have been the initial treatment of exertional dyspnea or chest pain [1,4]. The beneficial effects of b-blockers in patients with HCM are because of a decrease in heart rate, an improvement of ventricular filling during diastole, a decrease in myocardial oxygen demand, and a reduction of sympathetic tone [4]. Alternatively, verapamil has been used effectively in patients who either cannot tolerate a b-blocker (eg, Severe asthmatic) or have no initial response to beta-blockade. Verapamil should be prescribed with caution to patients with a large outflow gradient or pulmonary hypertension as its use in these patients may lead to severe Hemodynamic compromise [4]. Disopyramide, a class IA antiarrhythmic drug, used most often in conjunction with a b-blocker, has been used as an alternative to verapamil and may relieve symptoms through its negative inotropic properties [2,4]. If a patient develops signs of left ventricular systolic dysfunction (ie, congestive heart failure), afterload-reducing agents, b-blockers, digox- in, and judicious use of diuretics are indicated [1].

It is important to note that the administration of a b-blocker or verapamil to patients with HCM does not protect them from sudden death [2,4]. These agents should be used only to improve symptoms.

Nonpharmacologic therapies are reserved for the minority of patients with HCM who fail medical management. Surgical septal myomectomy has been performed to relieve LVOT obstruction since its introduction in 1958. Currently, a modified Morrow procedure termed extended myomectomy is performed at specialized centers with the additional goal of correcting the SAM of the mitral valve that contributes to the pathophysiology [15]. The benefits to surgical septal myomectomy are significant and include relief of symptoms and improved quality of life; however, the procedure requires a sternotomy, cardiopulmonary bypass, and carries a 1-month mortality of approximately 0%to 6% [15].

Alcohol septal ablation is a newer procedure that involves injection of a small amount of absolute alcohol into a septal perforator coronary artery after successful cannulation using a percutaneous transluminal catheter technique. This procedure produces a modest infarction of the myocardial septum that results in subsequent akinesis, septal thinning, and fibrosis [1,15]. Follow-up studies indicate significant reduction in LVOT pressure gradients. Complications include a short-term mortality of 0% to 4%, undesired backflow of alcohol into the left anterior descending coronary artery with subsequent larger infarc- tion, and a 9% to 38% incidence of complete heart block necessitating placement of a permanent pacemaker [1,15].

Unlike surgical septal myomectomy, the Long-term effects of alcohol septal ablation are unknown. This procedure has generally been reserved for patients who are older and have a higher surgical risk [1].

Complications

Arrhythmias are common in patients with HCM. Hypertrophic cardiomyopathy is associated with an in- creased incidence of Wolf-Parkinson-White syndrome. In addition, as many as 10% to 40% of patients with HCM experience chronic or Paroxysmal atrial fibrillation [2,16]. Patients with HCM who develop atrial fibrillation are at increased risk for systemic thromboembolism, heart failure, and death [2,4,16]. Predictors of atrial fibrillation in patients with HCM include left atrial enlargement and advanced age [16]. Although b-blockers or verapamil are usually effective at controlling the heart rate, patients with recurrent or chronic atrial fibrillation may benefit from amiodarone or atrioventricular node ablation [2]. Anticoagulant therapy should be started on all patients without contraindications who display recurrence of even brief episodes of atrial fibrillation [2,4].

Turbid blood flow in areas of obstruction as well as

mitral valve anomalies place patients with HCM at moderate risk for Infective endocarditis [17]. Appropriate antibiotic prophylaxis is warranted for patients undergoing dental or surgical procedures [1,17].

Conclusion

Hypertrophic cardiomyopathy is one of the most common inherited primary cardiac disorders. Despite previous over- estimations of the annual mortality attributed to HCM, it remains the most common cause of SCD in young athletic individuals. The presenting symptoms associated with HCM are variable owing in part to the significant genetic heterogeneity. Obtaining a detailed family history is essential to aid in risk assessment. The ECG will be abnormal in most patients with HCM. The most specific ECG abnormalities that emergency physicians should be aware of are concurrent LVH with deep narrow Q waves in the lateral leads. The diagnosis is currently confirmed by Doppler echocardiogra- phy, although ECG changes may be present before the echocardiogram is abnormal.

All patients suspected of having HCM should be referred to a cardiologist for further testing and risk assessment. Patients must be instructed to refrain from intense exercise while awaiting confirmation of the diagnosis. Medical therapy aims to improve the symptoms associated with LVOT obstruction and diastolic dysfunction, but does not protect against SCD with the exception of amiodarone. Patients with medically refractive symptoms may be considered for a surgical septal myomectomy or alcohol septal ablation. High-risk patients need prompt referral and evaluation for placement of a potentially life-saving AICD.

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