Abstract
BackgroundUltrasound myocardial cavitation enabled treatment (MCET) is an image-guided method for tissue reduction. In this study, a strategy of fractionated (multiple) treatments was tested for efficacy.MethodsDahl SS rats were anesthetized and prepared for treatment with a focused ultrasound transducer in a warm water bath. Aiming at the anterior left ventricular wall was facilitated by imaging with a 10 MHz phased array (10S, GE Vivid 7, GE Vingmed Ultrasound, Horten, Norway). MCET was accomplished at 1.5 MHz by pulse bursts of 4 MPa peak rarefactional pressure amplitude, which were intermittently triggered 1:8 from the ECG during infusion of a microbubble suspension for cavitation nucleation. Test groups were sham, a 200 s treatment, three 200 s treatments a week apart, and a 600 s treatment. Treatment outcome was observed by plasma troponin after 4 h, echocardiographic monitoring and histology at 6 wk.ResultsThe impacts of the fractionated treatments summed to approximately the same as the long treatment; e. g. the troponin result was 10.5 ± 3.2 for 200 s, 22.7 ± 5.4 (p < 0.001) for the summed fractionated treatments and 29.9 ± 6.4 for 600 s (p = 0.06 relative to the summed fractionated). While wall thickness was not reduced for the fractionated treatment, tissue strain was reduced by 35% in the target area relative sham (p < 0.001).ConclusionThe ability to fractionate treatment may be advantageous for optimizing patient outcome relative to all-or nothing therapy by surgical myectomy or alcohol ablation.
Highlights
Ultrasound myocardial cavitation enabled treatment (MCET) is an image-guided method for tissue reduction
Hypertrophic cardiomyopathy (HCM) can occur in several regions of the myocardium, and is troubling when restrictions occur in the left ventricular outflow tract (LVOT)
The fractionated treatment groups had quite similar trends of repeated before sacrifice) echocardiographic wall thickness, ejection fraction, wall strain and endocardial displacement determined from the echocardiographic images, the wall thickness measured in histological samples, and the percentage of fibrotic area seen in Masson’s trichrome slides within the target region
Summary
Ultrasound myocardial cavitation enabled treatment (MCET) is an image-guided method for tissue reduction. A strategy of fractionated (multiple) treatments was tested for efficacy. Hypertrophic cardiomyopathy (HCM) is a relatively common genetic cardiovascular disease, occurring in more than 1 in 500 people [1, 2]. HCM can occur in several regions of the myocardium, and is troubling when restrictions occur in the left ventricular outflow tract (LVOT). Patients may experience shortness of breath, angina, palpitations, and even sudden death in young athletes [3]. Hypertrophy leads to obstruction of the LVOT in up to 75% of patients, either at rest or with exercise. One-third of patients with obstruction remain symptomatic after pharmacological therapy and are candidates for myocardial reduction [4].
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