hypertrophic%20cardiomyopathy
HYPERTROPHIC CARDIOMYOPATHY

Hypertrophic cardiomyopathy is a genetically determined cardiac disorder characterized by hypertrophy, often of the left ventricle (LV), with nondilated ventricular chambers and no other cardiac or systemic disease (eg aortic stenosis, thyroid disease or hypertension) capable of producing the extent of hypertrophy manifested by the patient.

Symptoms can range from patients being asymptomatic to mildly or significantly symptomatic with pre-syncopal or syncopal episodes, palpitations, chest pain, decreased exercise tolerance, symptoms of pulmonary congestion (eg fatigue, dyspnea, orthopnea and paroxysmal nocturnal dyspnea) and symptoms of end-stage heart failure.

Approach to treatment is based on clinical experience and observational data as large randomized trials regarding medical therapy in hypertrophic cardiomyopathy are lacking.

An empiric therapy is often necessary to identify the best possible drug for the patient, starting at a low dose and titrating until clinical improvement or occurrence of side effects.

Treat comorbidities such as hypertension, diabetes, obesity and hyperlipidemia according to existing guidelines due to the significant influence of concomitant coronary artery disease on the survival of patients with hypertrophic cardiomyopathy.

 

Hypertrophic%20cardiomyopathy Diagnosis

History

  • Inquire from the patient symptoms related to angina, arrhythmias or heart failure
  • In the family history, review at least 3 generations focusing on events such as heart failure, cerebrovascular accidents particularly in those <50 years old, cardiac transplantation, defibrillator and pacemaker implants, and sudden cardiac death

Physical Examination

  • Patients examined demonstrate a pulse that rises and falls rapidly, prominent LV impulse, a fourth heart sound and an apical systolic murmur that increases with Valsalva maneuver
  • Examine also for extracardiac signs that may suggest a phenotypic mimic, eg cataracts and corneal opacities in Anderson-Fabry disease, gait disturbance in Friedreich ataxia

Laboratory Tests

  • Help in identifying conditions that lead to or aggravate ventricular dysfunction (eg diabetes mellitus, thyroid disease, renal dysfunction) and organ dysfunction developing from advanced heart failure
  • Include hemoglobin, fasting blood glucose, thyroid function tests, liver transaminases, renal function tests, creatine phosphokinase, troponin T and brain natriuretic peptide

Screening

12-Lead Electrocardiography (ECG)

  • Performed during the initial evaluation of patients with HCM, it is abnormal in 75-95% of such individuals
  • Major criteria include LV hypertrophy with repolarization changes, abnormal Q waves and inversion of T waves
    • Minor criteria include LV leads showing complete bundle branch block, interventricular conduction defect or minor repolarization changes, deep S V2, unexplained syncope, chest pain or dyspnea
    • Diagnosis of familial HCM is with 1 major criterion or 2 minor ECG criteria plus 1 minor echocardiographic criterion
  • Other findings may include the following:
    • Changes in P wave may suggest LBBB, left axis deviation or LA dilatation
    • PR interval that is short and QRS complex upstroke that is slurred may be seen in HCM with no underlying accessory pathways
    • Atrial fibrillation that is persistent is associated with a high risk of thromboembolism

Echocardiography

  • Reliably confirms HCM diagnosis
  • Aids in determining distribution and extent of hypertrophy, LV systolic and diastolic function, severity of outflow tract obstruction, pathology of membranes or valves (ie mitral regurgitation), and evidence of abnormal or anomalous papillary muscles
  • Major criteria include LV wall thickness in the anterior septum of ≥13 mm or posterior septum or free wall of ≥15 mm, severe systolic anterior motion of the mitral valve (SAM) (septal-leaflet contact)
    • Minor criteria include LV wall thickness in the anterior septum of 12 mm or posterior septum or free wall of 14 mm, moderate SAM (absent septal-leaflet contact), redundant leaflets of mitral valve
    • Diagnosis of familial HCM is with 1 major criterion or 2 minor echocardiographic criteria or 1 minor echocardiographic criterion plus 2 minor ECG criteria

Transthoracic Echocardiography

  • Recommended during baseline or screening examinations, for evaluation of prognosis during follow-up and after developing new cardiac symptoms or change in clinical status

Transesophageal Echocardiography

  • Aids in the evaluation of the mitral valve, ie mitral regurgitation
  • Used when planning for invasive septal reduction or surgical myectomy and assessing post-surgical complications

Contrast Echocardiography

  • Improves visualization of the endocardium and LV apex
  • Helps guide alcohol localization during alcohol septal ablation

Other Investigations

Holter Monitor and Exercise Test

  • The diagnosis of HCM may be confirmed or the risk of sudden death may be established with a 24- to 48-hour ambulatory Holter monitor or an exercise test that may be done with or without myocardial perfusion scanning or echocardiography; both tests can provide additional information on etiology and prognosis
    • Exercise test may reveal ischemia or arrhythmia
    • Holter monitoring may reveal a non-sustained ventricular tachycardia or paroxysmal atrial fibrillation and may help identify candidates for ICD therapy

Genetic Testing

  • All patients have to be counseled before and after genetic testing
  • May be performed in patients with signs and symptoms suggestive of HCM to verify diagnosis, those with an atypical clinical presentation of HCM or when HCM cannot be accounted solely by a non-genetic source
  • Identifies the gene mutation that causes the disease which can be used for genetic testing and eventual early management of at-risk family members and may also help in decision making regarding future reproduction
    • Female patients should be counseled regarding the risks associated with pregnancy and the risk of transmitting the disease to the fetus
  • A gene-positive detection rate of 40-50% may result from screening of the most common HCM-causing genes

Cardiac Biopsy

  • Rarely performed but shows features of HCM such as interstitial fibrosis and myocyte hypertrophy and disarray, though these are usually seen post-mortem
  • May be considered in cases where myocardial inflammation, infiltration or storage is suspected after evaluation with specialized tests

Imaging

Cardiac Magnetic Resonance Imaging (MRI)

  • Further determines the distribution and severity of hypertrophy and fibrosis
  • Aids in the diagnosis when findings are conflicting between an ECG and echocardiography
  • Helps in planning use of an implantable cardiac defibrillator (ICD)
  • Advantages over echocardiography include ability to quantify fibrosis using late gadolinium enhancement (LGE) and evaluation of areas not well seen on echocardiography such as apical HCM
    • Phenotypic mimics of HCM are diagnosed using cardiac MRI with LGE

Sudden Cardiac Death

  • HCM is the most common structural cause of sudden cardiac death in individuals <35 years old and competitive athletes
    • Sudden cardiac death can occur in 1% of patients annually
    • Happens most commonly in HCM during or immediately post exercise, though may also happen at rest
  • Major risk factors for sudden cardiac death include the following:
    • Family history of premature sudden cardiac death
    • Unexplained syncope
    • LV wall thickness ≥30 mm
    • Prior episodes of confirmed non-sustained ventricular tachycardia (≥3 beats at a rate ≥120 beats/minute) on ambulatory ECG
    • Prior cardiac arrest or ventricular tachycardia (secondary prevention)
  • Studies have also shown other risk modifiers to be considered in evaluating the risk of sudden cardiac death:
    • Age <21 years at presentation
    • Abnormal BP response to exercise (increase in SBP <20 mmHg, without rise, or a decrease in BP >20 mmHg during exercise, or a disproportionate decrease in BP immediately after exercise)
    • Increased size of left atrium
    • Presence of myocardial ischemia
    • LVOTO ≥30 mmHg at rest or with provocation
    • Presence of LGE on cardiac MRI
    • Presence of >1 mutation (double, compound, or triple mutations)
  • HCM Risk-SCD is a risk prediction model that calculates a patient’s 5-year risk of sudden cardiac death and it compared favorably with CHA2DS2-VASc scoring system
    • Recommended in patients >16 years old with no history of resuscitated ventricular tachycardia or fibrillation or spontaneous sustained ventricular tachycardia resulting in syncope or hemodynamic compromise
  • ICD is the only effective means of sudden cardiac death prevention and is recommended for patients with a life expectancy of >1 year, hemodynamically significant ventricular tachycardia, ventricular fibrillation or previously documented cardiac arrest
    • Should be considered in patients with ≥6% estimated 5-year risk of sudden cardiac death
    • Consider physician’s clinical judgment and the patient’s wishes when planning prophylactic ICD therapy based on above risk factors
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