Diagnostics

Hypertrophic cardiomyopathy: electrocardiographicmanifestations and other important considerationsfor 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, USAbDepartment of Emergency Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USAcDepartment of Emergency Medicine, University of Virginia, Charlottesville, VA 22911, USA

Received 16 April 2006; accepted 17 April 2006

Abstract Hypertrophic cardiomyopathy (HCM) is one of the most common inherited primary cardiacdisorders and the most common cause of sudden cardiac death in young athletes. With advances intechnology, 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 greatlyincrease the likelihood of sudden death if their disease remains undiagnosed. Therefore, it is imperativethat emergency physicians be familiar with the symptoms and typical electrocardiogram manifestations

of HCM. Three illustrative cases are presented with a review of the disease.D 2007 Elsevier Inc. All rights reserved.

1. Introduction

In the mid-19th century, French pathologists firstdescribed the pathology of a cardiac disorder known todayas hypertrophic cardiomyopathy (HCM). Because, in part,of the heterogeneity of this disease as well as technologicaladvances in genetic testing, HCM has become the preferredname, replacing previous names such as hypertrophicobstructive cardiomyopathy and idiopathic hypertrophicsubaortic stenosis, which described the typical, but notuniversal, features of left ventricular outflow tract (LVOT)obstruction and the predilection for asymmetrical hypertro-phy of the ventricular septum. Hypertrophic cardiomyopa-

thy accurately reflects the primary diagnostic feature of athickened myocardium without ventricular dilation inabsence of conditions known to secondarily result inventricular hypertrophy (eg, systemic hypertension andaortic stenosis).

Over the last 50 years, scientific interest has led toincreased understanding of this extremely variable disease.Hypertrophic cardiomyopathy is currently recognized to beone of the most common inherited diseases of the heart,occurring in as many as 1 in 500 individuals [1-4]. Earlystudies suggested annual mortality rates as high as 3% to 6%due largely to sudden cardiac death (SCD) in patients withHCM [1,3,4]. These early studies were primarily conductedat tertiary referral centers and included patients preferen-tially referred because of the severity of their symptoms [4].The annual mortality of unselected populations with HCMis estimated to be 1% to 2% [1,3,4].

0735-6757/$ – see front matter D 2007 Elsevier Inc. All rights reserved.

doi:10.1016/j.ajem.2006.04.017

* Corresponding author.

E-mail addresses: amalmattu@comcast.net (A. Mattu)8wb4z@virginia.edu (W.J. Brady).

American Journal of Emergency Medicine (2007) 25, 72–79

www.elsevier.com/locate/ajem

2. Case presentations

2.1. Case 1

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

Laboratory studies including one set of cardiac markerswere ordered on the patient and were all normal. A chestradiograph was also obtained and demonstrated a normalheart size and no abnormalities. The patient demonstratedno dysrhythmias while being monitored in the ED. He wasthen discharged, still asymptomatic, with instructions foroutpatient follow-up. Two days later, the patient collapsedwhile once again running to catch a bus. Paramedics werecalled immediately. When they arrived the patient wasunconscious, pulseless, and apneic. His cardiac rhythm wasventricular fibrillation (Fig. 2). Standard advanced lifesupport measures used by the paramedics and subsequentlyby ED staff were unsuccessful and the patient died. Atautopsy, significant hypertrophy of the ventricular septumwas noted. There was no evidence of a prior myocardialinfarction, nor was there evidence of coronary atheroscle-

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

2.2. Case 2

A 25-year-old man presented to the ED complaining ofsevere palpitations and severe lightheadedness with near-syncope while playing basketball. The symptoms lasted foronly 5 to 10 minutes before resolving with rest. The patientdenied any medical history, family history of medicalillness, drug use, or prior similar episodes. Upon arrival tothe ED, he was asymptomatic. His vital signs and hisphysical examination were normal. An ECG was obtained(Fig. 2) and interpreted by both an emergency physician anda 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 furtherevaluation of the episode of near-syncope and the abnormalECG. All laboratory studies, including serial cardiacenzymes, were normal. The chest radiograph was normalas well. Twenty-four hours of cardiac monitoring failed toreveal any dysrhythmias. The patient was then referred for aDoppler echocardiogram. There was no evidence of wallmotion abnormality that would normally be expected with aprior myocardial infarction, and the patient’s ejectionfraction was normal. However, the study did revealventricular septal hypertrophy with some LVOT obstruction,diagnostic of HCM. The patient was then prescribedb-blocker medications and discharged for outpatient fol-low-up with a cardiologist.

2.3. Case 3

A 29-year-old man presented to the ED complaining ofpalpitations 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.

Hypertrophic cardiomyopathy 73

symptoms persisted for 10 to 15 minutes before resolvingwithout any intervention. The patient reported that he hadpresented to the ED on 2 prior occasions in the past monthfor similar complaints: on the first visit, he experience anear-syncopal episode while mowing the lawn, and on thesecond visit he experienced a syncopal episode whilewatching television. Both of those episodes were precededby palpitations. He was discharged from the ED after thefirst visit after having an ECG and normal laboratorystudies. He was admitted to the ED observation unit duringthe second presentation, whereupon he underwent serialcardiac enzyme testing and cardiac monitoring. He wasdischarged after the negative workup and instructed tofollow up with a primary care physician, but he had not yetdone so. The patient denied any medical history, familyhistory of early cardiac disease, or drug use.

On the current visit, the patient remained asymptomaticat the time of ED arrival. His vital signs and physicalexamination, including cardiac examination, were normal.An ECG was obtained (Fig. 4). The ECG was interpreted bythe emergency physician as being highly suggestive ofHCM. Of note, there was no significant difference in theECG when it was compared with the ECGs from thepatient’s 2 prior visits. Each of the past ECGs had beeninterpreted (by separate cardiologists) as bNormal sinusrhythm, left ventricular hypertrophy, lateral myocardialinfarction of indeterminate age.Q The emergency physician

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

3. Discussion

3.1. Pathophysiology

The heterogeneity of HCM can largely be explainedthrough examination of the genetic mutations responsiblefor disease production. Hypertrophic cardiomyopathy isknown to result from variable penetrance of the mendeliandominant inheritance of mutations in genes that encodeproteins of the cardiac sarcomere. Laboratory studies haveimplicated more than 150 different mutations in multiplesarcomeric proteins with most the mutations occurring in thefollowing 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 havebeen linked to the HCM phenotype [5]. Studies performedon pedigrees of different genotypes have led to thediscovery that some mutations carry a benign prognosis,whereas other mutations result in early phenotypic diseaseexpression and worse prognosis.

Fig. 2 (Case 1) Ventricular fibrillation.

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

B.S. Kelly et al.74

Phenotypic manifestation of HCM is complicated furtherby factors such as modifier genes or environmentalinfluences [2]. These complexities result in the differentphenotypic manifestations of HCM even within familieswith the same genetic defect [3]. It therefore comes as nosurprise that the clinical presentation and disease course ishighly variable.

These genetic mutations result in LVH, which cannot beattributed to other commonly known etiologies. Themagnitude of hypertrophy is highly variable ranging frommild (13-15 mm) to severe (N30 mm) [2]. The distributionof hypertrophy is also variable, but is most often asymmetricand most pronounced in the anterior ventricular septum [2].Other patterns of hypertrophy associated with HCM includesymmetric or concentric LVH (~20%) and apical (~10%).Spontaneous increase in ventricular hypertrophy is commonduring periods of rapid growth and is most apparent inadolescence. Upon completion of adolescence, the magni-tude of hypertrophy often remains stable throughout adultlife but may paradoxically decrease.

Postmortem histologic examination of myocardial sam-ples in HCM reveals loss of the normal parallel myocytearchitecture, a condition known as myocyte disarray. Otherfindings include myocardial fibrosis, coronary artery abnor-malities including increased collagen deposition in thevessel walls, and narrowing of the arteriolar lumen. Thefeatures may serve as the substrate for arrhythmias in HCM.

Other abnormalities associated with HCM includemalformations of the mitral valve leaflets and severesystolic anterior motion (SAM) of the mitral valve. Theseabnormalities can lead to abnormal leaflet coaptation, mitralregurgitation, and additional LVOT obstruction.

3.2. Clinical presentation

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

especially, sudden cardiac death in a young relativeincreases the likelihood of HCM. In addition, because ofautosomal dominant inheritance, a family history of HCMgreatly 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 arenonspecific and include dyspnea, exercise intolerance,

dizziness, and near syncope or syncope. The severity ofthese symptoms may change throughout the day. Becauseof the dynamic nature of the degree of obstruction in HCM,

patients may be asymptomatic at rest, but may becomesymptomatic even with minimal exertion. In addition,

symptoms may worsen after large meals or alcoholingestion [3].

Chest pain is more common in younger patients and may

signal cardiac ischemia secondary to a mismatch in oxygensupply and demand to the thickened ventricle. In severehypertrophy, filling of the coronary arteries during diastole

may become compromised. In addition, coronary arteriolarnarrowing 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 HCMand may be related to decreases in blood pressure due toLVOT obstruction. Alternatively, syncope should alert theclinician to the possibility of episodic atrial or ventriculararrhythmias, especially when it occurs in association withpalpitations [3]. It is believed that children who presentwith syncope secondary to suspected HCM represent aparticularly high-risk group and should receive aggressiveinitial evaluation.

Unfortunately, SCD may be the initial and onlymanifestation of disease, with the diagnosis of HCM madeat postmortem examination after the death of a previously

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

Hypertrophic cardiomyopathy 75

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

Physical examination is more likely to be abnormal inpatients with LVOT obstruction. Palpation of the carotidartery may reveal an initial brisk upstroke with subsequentcollapse and secondary rise in late systole because ofdynamic LVOT obstruction. Examination of the precordiummay reveal a nondisplaced, hyperdynamic point of maximalimpulse or a double apical impulse during systole as thehypertrophied noncompliant left ventricle contracts force-fully. Less commonly, a triple apical impulse may occursecondary to the addition of a palpable atrial gallop. An S4gallop may be heard during atrial systole.

The classic description of the cardiac murmur in HCMreferred to patients with subaortic obstruction only and maybe present in as few as 30% to 40% of patients [7]. In thesepatients, auscultation may reveal a harsh crescendo-decrescendo systolic ejection murmur, which is bestappreciated at the apex and radiates to the sternal notch.The intensity of the murmur is increased by maneuvers thatdecrease preload such as standing, Valsalva maneuver, oramyl nitrite administration. The murmur of HCM is uniquefrom nearly all other cardiac murmurs in that it increaseswith Valsalva, making the performance of this maneuververy important during cardiac examination. In patients withconcurrent mitral valve abnormalities, a holosystolicmurmur that radiates to the axilla may be appreciated,reflecting mitral regurgitation.

3.3. Diagnosis

Once the diagnosis of HCM is considered, the workupshould generally include a chest x-ray, an ECG, and atransthoracic echocardiogram with Doppler examination. Ofthese examinations, the ECG and echocardiogram have thehighest yield, as the chest x-ray will likely be normal, but

may be helpful for ruling out other conditions. Unlike manyother 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 ofthe complex, time-consuming, and cost-prohibitive nature ofgenetic 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 abnormaleven when echocardiography fails to demonstrate hypertro-phy [3,8,10]. The ECG findings present in patients withHCM depend on the pattern and extent of myocardialhypertrophy. Characteristic findings of LVH are commonand include high-voltage R waves in the anterolateral leads(V4, V5, V6, I, and aVL) [3,6,9,11]. Prominent R waves maybe present in leads V1 and V2 as well [12]. The most frequentabnormalities found are large-amplitude QRS complexesconsistent with LVH and associated ST-segment and T-wavechanges [1,13]. Deep, narrow Q waves are common in theinferior (II, III, aVF) and lateral (I, aVL, V5, and V6) leads inpatients with septal hypertrophy and may mimic myocardialinfarction [3,6,9,11]. The morphology of the Q waves—deepand very narrow—is perhaps the most characteristic andspecific finding of HCM. Although often these Q waves aremistaken for those of myocardial infarction, it should berecognized that infarction-related Q waves are wider, at least0.04 seconds (ie, at least 1 mm wide on standard ECGpaper). The Q waves of HCM are rarely this wide. In theauthors’ experience, deep narrow Q waves in the lateral leadsare much more common than in the inferior leads. TheseQ waves may appear in all of the lateral leads—I, aVL, V5,and V6 (Fig. 1); they may predominate in just leads I andaVL (Fig. 4); or they may predominate in just leads V5 andV6 (Fig. 5). Although large-amplitude QRS complexes arethe most common finding in HCM, deep narrow Q waves inthe lateral leads are the most specific finding and should

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

B.S. Kelly et al.76

immediately prompt a high degree of suspicion when theyare found. A less common variant of HCM involves isolatedapical hypertrophy. Patients with apical HCMwill frequentlyhave deeply inverted T waves in the mid and lateralprecordial leads (Fig. 6) [1,3,6,9].

Shimizu et al examined the chronological ECG changesin carriers with the deletion of lysine 183 (Lys183del) in thecardiac troponin I (cTnI) gene compared with noncarriersand found abnormal Q waves in leads I, II, III, aVF, V5, andV6 were frequently observed during the early teenage years.In contrast, carriers of the Lys183del in cTnI older than20 years were more likely to demonstrate abnormal Q wavesprimarily in I, aVL, and other lateral leads. They concludedthat sensitivity, specificity, positive predictive value, andnegative predictive value of abnormal Q waves in the teensof their study population was 67%, 100%, 100%, and 78%,respectively [13].

The transthoracic echocardiogram is one of the mostuseful tests in patients with HCM. It can document anumber of findings including the degree of hypertrophy,systolic or diastolic dysfunction, the presence of LVOT ormid-ventricular obstruction, and mitral valve abnormalitiesincluding the degree of SAM. Most patients with HCM havevarying degrees of diastolic dysfunction. Systolic dysfunc-tion is rare in the early course of the disease, but as thedisease progresses to generalized dilated cardiomyopathyover the course of many years, systolic dysfunctionbecomes common as well. The direction and degree ofmitral regurgitation, if present, can also be documented. Theaddition of Doppler studies is important to correctly identifyoutflow obstruction and mitral regurgitation. Patientswithout obstruction at rest should undergo repeat Doppler

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

3.4. Sudden cardiac death

Sudden cardiac death is the most feared complication ofHCM. It is an evolving topic of intense investigation. Severalclinically useful risk factors have been identified. Thepredictive value of each factor is low; thus, a collective riskprofile, created by accurate assessment of individual riskfactors, is the best method to identify high-risk patients [5].

Individual risk factors for SCD include prior cardiacarrest, episodes of sustained ventricular tachycardia, recur-rent syncope, especially when associated with exertion, afamily history of 1 or more SCDs, extreme LVH (maximumwall thickness N30-35 mm), the presence of LVOT gradientN30 mm Hg, an abnormal blood pressure response duringexercise, and the presence of nonsustained ventriculartachycardia during ambulatory ECG monitoring [2,4,5,14].Collectively, a risk profile with 2 or more individual riskfactors suggests a high annual risk of SCD.

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

3.5. Management options

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

Fig. 6 Apical hypertrophic cardiomyopathy. Normal sinus rhythm with LVH and deeply inverted T waves in the mid and lateral precordialleads. T wave abnormality is also present in the inferior leads in this patient.

Hypertrophic cardiomyopathy 77

therefore extremely important to recommend that anypatient suspected of having HCM avoid all intense,competitive, or isometric activity. In general, light aerobicexercise such as walking or noncompetitive swimming, isconsidered safe [1].

Treatment strategies aim to improve or relieve thesymptoms caused by LVOT obstruction or abnormalventricular function due to diastolic dysfunction. Tradition-ally, b-blocker medications have been the initial treatmentof exertional dyspnea or chest pain [1,4]. The beneficialeffects of b-blockers in patients with HCM are because of adecrease in heart rate, an improvement of ventricular fillingduring diastole, a decrease in myocardial oxygen demand,and a reduction of sympathetic tone [4]. Alternatively,verapamil has been used effectively in patients who eithercannot tolerate a b-blocker (eg, severe asthmatic) or have noinitial response to beta-blockade. Verapamil should beprescribed with caution to patients with a large outflowgradient or pulmonary hypertension as its use in thesepatients may lead to severe hemodynamic compromise [4].Disopyramide, a class IA antiarrhythmic drug, used mostoften in conjunction with a b-blocker, has been used as analternative to verapamil and may relieve symptoms throughits negative inotropic properties [2,4]. If a patient developssigns of left ventricular systolic dysfunction (ie, congestiveheart 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 ab-blocker or verapamil to patients with HCM does notprotect them from sudden death [2,4]. These agents shouldbe used only to improve symptoms.

Nonpharmacologic therapies are reserved for the minorityof patients with HCM who fail medical management.Surgical septal myomectomy has been performed to relieveLVOTobstruction since its introduction in 1958. Currently, amodified Morrow procedure termed extended myomectomyis performed at specialized centers with the additional goal ofcorrecting the SAM of the mitral valve that contributes to thepathophysiology [15]. The benefits to surgical septalmyomectomy are significant and include relief of symptomsand improved quality of life; however, the procedurerequires a sternotomy, cardiopulmonary bypass, and carriesa 1-month mortality of approximately 0%to 6% [15].

Alcohol septal ablation is a newer procedure thatinvolves injection of a small amount of absolute alcoholinto a septal perforator coronary artery after successfulcannulation using a percutaneous transluminal cathetertechnique. This procedure produces a modest infarction ofthe myocardial septum that results in subsequent akinesis,septal thinning, and fibrosis [1,15]. Follow-up studiesindicate significant reduction in LVOT pressure gradients.Complications include a short-term mortality of 0% to 4%,undesired backflow of alcohol into the left anteriordescending coronary artery with subsequent larger infarc-tion, and a 9% to 38% incidence of complete heart blocknecessitating placement of a permanent pacemaker [1,15].

Unlike surgical septal myomectomy, the long-term effects ofalcohol septal ablation are unknown. This procedure hasgenerally been reserved for patients who are older and havea higher surgical risk [1].

3.6. Complications

Arrhythmias are common in patients with HCM.Hypertrophic cardiomyopathy is associated with an in-creased incidence of Wolf-Parkinson-White syndrome. Inaddition, as many as 10% to 40% of patients with HCMexperience chronic or paroxysmal atrial fibrillation [2,16].Patients with HCM who develop atrial fibrillation are atincreased risk for systemic thromboembolism, heart failure,and death [2,4,16]. Predictors of atrial fibrillation in patientswith HCM include left atrial enlargement and advanced age[16]. Although b-blockers or verapamil are usually effectiveat controlling the heart rate, patients with recurrent orchronic atrial fibrillation may benefit from amiodarone oratrioventricular node ablation [2]. Anticoagulant therapyshould be started on all patients without contraindicationswho display recurrence of even brief episodes of atrialfibrillation [2,4].

Turbid blood flow in areas of obstruction as well asmitral valve anomalies place patients with HCM at moderaterisk for infective endocarditis [17]. Appropriate antibioticprophylaxis is warranted for patients undergoing dental orsurgical procedures [1,17].

4. Conclusion

Hypertrophic cardiomyopathy is one of the most commoninherited primary cardiac disorders. Despite previous over-estimations of the annual mortality attributed to HCM, itremains the most common cause of SCD in young athleticindividuals. The presenting symptoms associated with HCMare variable owing in part to the significant geneticheterogeneity. Obtaining a detailed family history is essentialto aid in risk assessment. The ECG will be abnormal in mostpatients with HCM. The most specific ECG abnormalitiesthat emergency physicians should be aware of are concurrentLVH with deep narrow Q waves in the lateral leads. Thediagnosis is currently confirmed by Doppler echocardiogra-phy, although ECG changes may be present before theechocardiogram is abnormal.

All patients suspected of having HCM should be referredto a cardiologist for further testing and risk assessment.Patients must be instructed to refrain from intense exercisewhile awaiting confirmation of the diagnosis. Medicaltherapy aims to improve the symptoms associated withLVOT obstruction and diastolic dysfunction, but does notprotect against SCD with the exception of amiodarone.Patients with medically refractive symptoms may beconsidered for a surgical septal myomectomy or alcoholseptal ablation. High-risk patients need prompt referral andevaluation for placement of a potentially life-saving AICD.

B.S. Kelly et al.78

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