Measuring Left Ventricular Outflow Tract Signal Gradient in Hypertrophic Cardiomyopathy

Chief complaint: Chest pain and dyspnea on exertion.

History of present illness: A 61-year-old woman presents for preoperative evaluation prior to a cosmetic procedure. She reports persistent exertional dyspnea and chest discomfort for the prior year. Her chest discomfort is substernal in location, burning in nature, and radiating to the left side. Her symptoms are episodic, occur with moderate exertion, last 10-20 min, and resolve with rest. She underwent coronary angiography in the prior year for similar symptoms, which showed right coronary artery (RCA) stenosis that was treated with a drug-eluting stent; however, mild symptoms have persisted since.

Past medical history: Coronary artery disease with a prior RCA percutaneous coronary intervention, hypertension, gastroesophageal reflux disease, nephrolithiasis

Past surgical history: Cesarean section

Family history: No significant family history is known; father and mother died of unknown disease in old age

Medications: Aspirin, ticagrelor, atorvastatin, metoprolol succinate

Physical examination findings:
Height: 1.5 m
Weight: 74 kg
Body mass index: 33 kg/m2
Blood pressure (BP): 143/86 mm Hg
Heart rate (HR): 65 bpm
Respiratory rate: 14 breaths/min
Temperature: 35.67°C
General appearance: Comfortable
Head and neck: Jugular venous pressure 6 cm H2O and normal carotid upstroke
Chest: Clear lung fields
Cardiac examination: Nondisplaced point of maximal impulse, regular rate and rhythm, grade 2/6 soft systolic murmur auscultated in the left second intercostal space and increased with a squat-to-stand maneuver
Abdomen: Soft, nontender, nondistended
Extremities: Warm and well perfused; no peripheral edema
Neurologic: Alert and oriented, without any focal deficits
Electrocardiography: Sinus rhythm; left ventricular hypertrophy (LVH) with repolarization abnormalities, including T-wave inversions in the lateral and high lateral leads (Figure 1)

Figure 1

Figure 1

Echocardiography: Severe concentric LVH (interventricular septum diameter 1.7 cm, left ventricular [LV] posterior wall diameter 1.8 cm), small LV cavity size, hyperdynamic LV function with LV ejection fraction 75% (Figures 2, 3)

Figure 2

Figure 2
PLAX view showing LVH.

LVH = left ventricular hypertrophy; PLAX = parasternal long-axis.

Figure 3

Figure 3
Apical five-chamber view showing trace MR and minimal turbulence in the LVOT.

LVOT = left ventricular outflow tract; MR = mitral regurgitation.

Doppler echocardiography at rest: Trace mitral regurgitation (MR), no MR signal; left ventricular outflow tract (LVOT) velocity 2 m/sec and LVOT gradient 16 mm Hg (Figure 4)

Figure 4

Figure 4
(Panel A) PLAX view in midsystole (arrow pointing toward the anterior mitral leaflet). (Panel B) Apical five-chamber view in midsystole (arrow pointing toward anterior mitral leaflet). (Panel C) Color Doppler in apical five-chamber view showing mild MR (thin arrow) and mild turbulence in the LVOT (thick arrow). (Panel D) CW Doppler in the LVOT, showing velocity 2 m/sec (i.e., 16 mm Hg gradient at rest).

CW = continuous-wave; LA = left atrium; LV = left ventricle; LVOT = left ventricular outflow tract; MR = mitral regurgitation; PG = pressure gradient; PLAX = parasternal long-axis.

These findings are consistent with symmetric concentric hypertrophic cardiomyopathy (HCM) with mild systolic anterior motion (SAM) and mild resting gradient of 16 mm Hg. In patients with hypertrophic obstructive cardiomyopathy (HOCM), the severity of obstruction can be highly variable depending on multiple factors such as BP, preload, and HR, among others. In those with suspected obstruction and a resting LVOT gradient <30 mm Hg, provocative maneuvers are indicated (e.g., Valsalva or an exercise echocardiogram).

Stress echocardiography is performed next to assess the exercise LVOT gradient for evaluation of obstructive physiology because the patient has ongoing exertional symptoms. After 8.3 METs of exercise per the modified Bruce protocol, she develops dyspnea. Echocardiography at this time shows no wall motion abnormalities and images are obtained for evaluation of exercise-related hemodynamics (Figure 5). Poststress maximal HR is 131 bpm; however, it drops to 72 bpm by the time imaging is performed.

Figure 5

Figure 5
Apical four-chamber view showing worsened LVOT turbulence and posterolaterally directed MR after peak stress.

LVOT = left ventricular outflow tract; MR = mitral regurgitation.

Poststress imaging shows worsened LVOT obstruction and MR. Poststress BP is 145/93 mm Hg. A continuous-wave (CW) Doppler is obtained at this point (Figure 6).

Figure 6

Figure 6
(Panel A) Apical four-chamber view (arrow pointing toward SAM). (Panel B) Apical four-chamber view with color Doppler showing worsened LVOT gradient (long arrow) and MR (short arrow). (Panel C) CW Doppler signal at peak stress, with maximal velocity and calculated pressure gradient.

BP = blood pressure; CW = continuous-wave; LA = left atrium; LV = left ventricle; LVOT = left ventricular outflow tract; MR = mitral regurgitation; RV = right ventricle; SAM = systolic anterior motion; V = velocity.

What is the estimated LVOT gradient in this patient at peak stress?

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