Intracavitary Pressure Wire and Intravascular Ultrasound for the Evaluation of Combined Symmetric Hypertrophic Cardiomyopathy

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J INVASIVE CARDIOL 2008;20;E171-E173

Hypertrophic obstructive cardiomyopathy (HOCM) and aortic stenosis (AS) both result in congestive heart failure symptoms, syncope and chest pain.^1–3 In the elderly patient, when the two conditions coexist, distinguishing their relative contributions to the clinical presentation poses both a diagnostic and therapeutic challenge. Precise quantitative and qualitative assessment of the AS and left ventricular intracavitary gradients are essential in guiding the decision whether to proceed with aortic valve replacement versus ethanol septal ablation or septal myectomy, or both.³ If the AS is overestimated and the contribution of HOCM is underappreciated, aortic valve replacement would result in decreased afterload and increased left ventricular outflow tract gradient. This, in turn, could lead to a worsening gradient and obstruction. We describe a patient with HOCM combined with AS who underwent intracavitary pressure- wire evaluation and intravascular ultrasound (IVUS) and was subsequently treated with ethanol septal ablation after the predominant lesion was determined to be HOCM.
Case Report. An 80-year-old male with a medical history of hypertension, coronary artery disease status post coronary stenting to the right coronary artery and left anterior descending artery, symmetric HOCM, and mild AS presented with progressive dyspnea and chest discomfort upon exertion. A transthoracic echocardiogram (TTE) 1 month prior to admission revealed symmetric hypertrophic cardiomyopathy (septal thickness of 15 mm and lateral wall thickness of 12 mm) with a resting left ventricular outflow tract gradient of 36 mmHg, which increased to 188 mmHg with Valsalva. The patient also had AS with a peak gradient of 36 mmHg. The contribution of the aortic valve and outflow tract to the observed gradient was unclear. A repeat cardiac catheterization was performed to evaluate these symptoms and revealed patent coronary stents and no significant obstructive coronary artery disease.
During left-heart catheterization, the resting peak-to-peak gradient was 30 mmHg. Post-PVC, a prominent Brockenbrough- Braunwald sign was noted. At 5 mcg/kg/minute of dobutamine, concurrent TTE demonstrated an increase in the peak left ventricular outflow tract gradient to 100 mmHg and systolic anterior motion of the mitral leaflet.

To distinguish the respective contributions of AS and left ventricular outflow tract obstruction, a pressure wire (Radi Medical Systems, AB, Sweden) was advanced to the left ventricular apex and pullback pressures were measured (Figure 1). Approximately 70 mmHg of the gradient was attributable to the left ventricular outflow tract obstruction and 30 mmHg to the valvular aortic stenosis (Figures 2 and 3). To further define the anatomic nature of the gradient, IVUS (Atlantis PV, Boston Scientific Corp., Natick, Massachusetts) was used to image the left ventricular outflow tract and aortic valve (Figures 1,4 and 5). IVUS revealed mitral valve encroachment on the left ventricular outflow tract with systolic anterior motion of the mitral leaflet, and only mild restriction of the aortic valve opening (Figures 4 and 5). Given these findings, ethanol septal ablation was performed with echocardiographic guidance (Figure 6) and postprocedure TTE revealed a decrease in the left ventricular outflow tract gradient to 10 mmHg at rest. At 6 months post procedure, the patient remains asymptomatic with no limitations in activity.

Discussion. This case study illustrates a novel application of IVUS and pressure wire evaluation as a means of assessing left ventricular outflow tract obstruction as well as aortic valve stenosis. Although IVUS was previously used for preoperative assessment of stenotic aortic valves,⁴ its use to assess the outflow tract has not been reported. The combination of IVUS with pressure wire evaluation confirmed the dominant contribution of outflow obstruction to the gradient. The pressure wire was used to enable slow pullback without causing ectopy and gradient accentuation and to accurately position the sensor distal to the outflow tract obstruction and proximal to the aortic valve, with accurate measurements of corresponding pressures.
Percutaneous ethanol septal ablation has been employed in the treatment of moderate-to-severe symptomatic asymmetrical septal hypertrophy and has become a well-established, lessinvasive alternative to surgical septal myomectomy.^5–8 Its use in more symmetrical hypertrophy complicated by an outflow tract or mid-cavitary gradient has not been well described, but appears to result in resolution of the gradient, particularly if echocardiographic guidance targets the septal area responsible for the gradient where the mitral leaflets encroach on the outflow tract. As the population ages, aortic stenosis and longstanding left ventricular hypertrophy is frequently accompanied by an outflow tract or mid-cavitary dynamic gradient that often contributes to symptoms.^9–13 Ethanol septal ablation could provide symptomatic relief if medical therapy fails and the aortic stenosis is mild. IVUS and pressure-wire evaluation may become helpful in defining major pathology.

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