Contrasting anatomical consequences of extended surgical septal myectomy shown in the short-axis plane (A) and alcohol septal ablation (B). (A) The tissue resected at myectomy is from the left ventricular side of the basal anterior septum. (B) The tissue necrosis resulting from alcohol ablation is usually transmural and located more posteriorly and inferiorly in the basal anterior septum than is the case for myectomy. At midventricular level (lower row of B), the tissue necrosis involves the inferior septum either with transmural distribution or predominantly the right ventricular portion of the septum.

Short-axis plane cardiovascular magnetic resonance (CMR) image of the basal left ventricle (LV) from 3 hypertrophic cardiomyopathy patients showing the area of septal myectomy before (left), 3 to 7 days after surgery (center), and also 3 to 7 days after myectomy after the administration of gadolinium (right). Arrows show the area and extent of the muscular septal resection. In the post-gadolinium images, normal myocardium appears dark and necrotic (infarcted) myocardium appears white. There is no evidence of intramyocardial delayed hyperenhancement at or near the myectomy site, indicating the absence of necrotic tissue. RV = right ventricle.

Short-axis plane cardiovascular magnetic resonance (CMR) image of the basal left ventricle (LV) from 3 hypertrophic cardiomyopathy patients showing pre-ablation morphology (left panels) and the area of the septal ablation created by infusion of alcohol on the post-gadolinium images (center, right panels). The images in the right panel are identical to those in the center panel and highlight the area of the infarct with broken lines. Post-ablation images (after gadolinium) show large areas of transmural hyperenhancement with irregular borders, indicative of necrotic tissue (white) in the region of the targeted ablation. Arrow shows an inhomogeneous area within the core of an infarct in which gadolinium uptake is absent because of severe microvascular obstruction (center patient). RV = right ventricle.

Long-axis cardiovascular magnetic resonance (CMR) image views after alcohol septal ablation on a post-gadolinium study. There is sparing of the proximal basal septum (white arrow). The region of the hyperenhancement involves mainly the right ventricular side of the ventricular septum (black arrows). This patient had the most proximal septal perforator cannulated with apparent localization to the basal septum on contrast echocardiography during the ablation procedure. LA = left atrium; LV = left ventricle.

Top panels show long-axis cardiovascular magnetic resonance (CMR) imaging views before (left) and after (right) septal myectomy. The portion of basal septum evident in this plane, projecting into the left ventricular (LV) outflow tract, has been resected at myectomy (arrows). Bottom panels show long-axis views before (left) and 5 months after (right) septal ablation. The ablation has spared the most proximal portion of basal septum at the level of systolic anterior motion and mitral valve-septal contact, involving only the more distal septum below this level of obstruction (arrows). AML = anterior mitral leaflets; Ao = aorta; LA = left atrium; RV = right ventricle.