Hypertrophic obstructive cardiomyopathy

Primary genetic cardiomyopathy characterized by left ventricular hypertrophy not explained solely by hemodynamic loading conditions.

Definition

Primary genetic cardiomyopathy characterized by left ventricular hypertrophy not explained solely by hemodynamic loading conditions, with predominantly asymmetric septal involvement producing dynamic systolic outflow obstruction in the left ventricular outflow tract (LVOT) due to systolic anterior motion (SAM) of the mitral valve [C1] [G5-01] [G5-10] [G5-11].

Severity criteria

Mild (L): Resting peak trans-LVOT gradient < 30 mmHg (non-obstructive pattern at rest or minimal/absent baseline gradient; latent obstruction only inducible with provocative maneuvers) [C1] [G5-01].
Moderate (M): Resting peak trans-LVOT gradient 30–49 mmHg (hemodynamically evident obstruction at rest but below standard invasive intervention threshold) [C1] [G5-01].
Severe (G): Resting peak trans-LVOT gradient ≥ 50 mmHg (severe hemodynamically significant obstruction, formal threshold indicating septal reduction therapy in presence of refractory symptoms) [C1] [G5-01].

Findings by layer

Hemodynamics

Peak LV outflow tract gradient: L < 30 mmHg, M 30–49 mmHg, G ≥ 50 mmHg [C1] [G5-01].
Left ventricular end-diastolic pressure and pulmonary capillary wedge pressure: Elevated in moderate and severe stages due to diastolic dysfunction and hypertrophy [C1] [G5-10].

Rhythm

Normal sinus rhythm [C1] [G5-01].
Atrial fibrillation as a common supraventricular arrhythmia associated with elevated left atrial pressures [C1] [G5-01].

ECG

Left ventricular hypertrophy voltage criteria (left ventricular hypertrophy voltage criteria, positive Sokolow-Lyon / Cornell) accompanied by secondary ventricular repolarization abnormalities / systolic overload (LV systolic overload pattern) [E1] [C1].
Pathological pseudo-infarct Q waves (pseudoinfarct Q waves): Deep, narrow Q waves (< 40 ms) in inferolateral leads (I, aVL, V4–V6, II, III, aVF) resulting from initial depolarization forces of the massively thickened septum [C1] [G5-01] [G5-10].

Heart sounds and murmurs

Ejection mesosystolic murmur: Harsh diamond-shaped (crescendo-decrescendo) systolic murmur, loudest at lower left sternal border and apex; characteristically does not radiate to neck / carotids (key clinical distinction from fixed aortic stenosis) [B1] [G5-10] [G1-14].
Mitral regurgitation murmur: Accompanying apical holosystolic murmur of mitral incompetence due to SAM, with regurgitant jet directed eccentrically posterolaterally [G5-11].
Fourth heart sound (S4): Prominent presystolic atrial gallop at apex due to atrial contraction against a stiff, poorly compliant ventricle [G1-13] [G5-10].

Arterial pulse

Carotid pulse with spike-and-dome contour (pulsus bisferiens / spike-and-dome): Rapid, brisk initial upstroke corresponding to initial pre-obstructive ejection, followed by a mid-systolic dip due to dynamic obstruction and a second, more sustained late rise [B4] [G5-10].

Jugular venous pulse

Prominent 'a' wave: Caused by increased resistance to right ventricular filling when the hypertrophied septum bulges into the RV lumen (Bernheim effect) [B3] [G5-10].

Maneuvers

Valsalva maneuver (strain phase): Markedly increases murmur intensity by reducing preload and ventricular end-diastolic volume, narrowing the LVOT and accentuating SAM [B1] [G5-10].
Abrupt standing: Increases the murmur by decreasing preload [B1].
Squatting: Decreases murmur intensity by increasing venous return and arterial afterload, widening the LVOT cavity [B1].
Isometric handgrip: Decreases murmur intensity by increasing systemic vascular resistance (afterload), moving the anterior mitral leaflet away from the septum [B1].

Simulator severity grades

Simulator severity grades: Mild, Moderate, Severe

Baseline rhythm: Normal Sinus Rhythm

Also known as: Hypertrophic obstructive cardiomyopathy · Obstructive hypertrophic cardiomyopathy · Idiopathic hypertrophic subaortic stenosis · IHSS · HOCM

Other pathologies in this group

Related clinical comparisons

Compare with Calcific aortic stenosis →

Sources

[B1] Bedside diagnosis of systolic murmurs . N Engl J Med (1988) . DOI: 10.1056/NEJM198806163182404 PubMed: 2897627
[B3] The jugular venous pressure revisited . Cleve Clin J Med (2013) . DOI: 10.3949/ccjm.80a.13039 PubMed: 24085809
[B4] The Carotid Pulse . Clinical Methods: The History, Physical, and Laboratory Examinations (1990) . PubMed: 21250154
[C1] 2023 ESC Guidelines for the management of cardiomyopathies . Eur Heart J (2023) . DOI: 10.1093/eurheartj/ehad194 PubMed: 37622657
[E1] AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part V: electrocardiogram changes associated with cardiac chamber hypertrophy: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society: endorsed by the International Society for Computerized Electrocardiology . Circulation (2009) . DOI: 10.1161/CIRCULATIONAHA.108.191097 PubMed: 19228820
[G1-13] The Fourth Heart Sound . Clinical Methods: The History, Physical, and Laboratory Examinations (1990) . PubMed: 21250185
[G1-14] Systolic Murmurs . Clinical Methods: The History, Physical, and Laboratory Examinations (1990) . PubMed: 21250186
[G5-01] 2020 AHA/ACC Guideline for the Diagnosis and Treatment of Patients With Hypertrophic Cardiomyopathy: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines . Circulation (2020) . DOI: 10.1161/CIR.0000000000000937 PubMed: 33215931
[G5-10] Hypertrophic cardiomyopathy . Lancet (2013) . DOI: 10.1016/S0140-6736(12)60397-3 PubMed: 22874472
[G5-11] Systolic anterior motion begins at low left ventricular outflow tract velocity in obstructive hypertrophic cardiomyopathy . J Am Coll Cardiol (2000) . DOI: 10.1016/s0735-1097(00)00830-5 PubMed: 11028493