Intracardiac Echocardiography Guidance for Alcohol Septal Ablation in Hypertrophic Obstructive Cardiomyopathy

In this report, we describe the use of intracardiac echocardiography (ICE) to monitor and guide alcohol septal ablation in a patient with HOCM. Technical procedural insights are discussed. In addition, potential procedure-related risks and alternative therapeutic approaches are also highlighted.

Case Report. A 17-year-old female with HOCM was referred to our hospital for percutaneous alcohol septal ablation. She was in New York Heart Association (NYHA) functional class III (refractory to verapamil and propranolol) and had previously required automatic defibrillator implantation for recurrent syncope and a family history of sudden death. Transthoracic echocardiography (TTE) revealed a dynamic gradient of 110 mmHg at the left ventricular outflow tract starting at the mid-ventricular level, and severe mitral regurgitation. Coronary angiography was normal, but a severe “milking” effect was apparent on the mid segment of the posterior descending coronary artery causing its complete disappearance during systole. Both TTE and ICE (10.5 Fr, 5.5–10 MHz catheter [Acuson Corp., Siemens, Mountain View, California]) were used to guide the procedure. ICE provided striking, high-quality images of the left ventricle, including a complete visualization of the interventricular septum and systolic motion of the anterior mitral valve (Figures 1 A, B and C). A normal but severely hypertrophied papillary muscle was also demonstrated. Turbulent flow in the left ventricular outflow tract was nicely depicted on color Doppler ICE that also revealed the jet of mitral regurgitation in the left atrium. Contrast injection in the first septal branch was associated with partial opacification of the moderator band and the upper right endocardial surface of the septum, while most of the anterior septum remained unaffected (Figure 1D). A subsequent injection of contrast in the second septal branch enlightened the mid part of the septum, but slightly below the mitral-septal contact region (Figures 1 E and F). A perfect match was demonstrated between TTE and ICE findings regarding contrast location. Due to the absence of additional septal branches and the presence of an associated mid-cavity gradient, alcohol (3 ml) was eventually injected in this location despite recognizing that it was suboptimal. The catheter-measured gradient fell from 105 to 80 mmHg. At the end of the procedure, a mild type-A coronary dissection was noticed at the superior aspect of the left main coronary artery. This finding was attributed to a “to-and-fro” movement of the guiding catheter tip as a result of its unsteady sitting and hyperdynamic cardiac motion. The intervention resulted in a confined septal myocardial infarction (peak CPK = 780 IU). The patient was discharged 3 days later after an uneventful hospital stay.

At 1-year follow up the patient had clinically improved to NYHA functional class II. However, despite a clear reduction in the severity of mitral regurgitation, a significant gradient persisted at the left ventricular outflow tract on TTE. Discussion. The use of TTE during alcohol septal ablation has been advocated to guide the procedure. This technique allows visualization of the distribution of the echocardiographic agent in the myocardium after direct injection from the selected septal branch.^4–8 This is of major interest because previous reports emphasize the potential of the first septal branch to perfuse myocardial segments remote from the target upper anterior septum.⁹ In some cases, this has been associated with major complications, including large or remote myocardial infarction and severe mitral regurgitation as the result of papillary muscle necrosis.^4–8 Echocardiography enables ready detection of the enlightened myocardium just at the area of mitral-septal contact, which creates the intraventricular gradient. After echocardiographic guidance, the alcohol can be safely injected in the selected septal branch, ensuring that the resulting necrosis will be precisely located at the desired myocardial segment.^4–8

Our findings suggest the value of ICE for guidance of alcohol ablation in patients with HOCM. ICE is readily performed in this setting and provides unique, high-quality images of the entire interventricular septum and adjacent structures. This includes the mitral valve and papillary muscles. This information is of major interest since a severely hypertrophied papillary muscle or an abnormal papillary muscle may constitute a contraindication for this procedure.¹⁰ Contrast location is accurately detected by ICE and color Doppler may also be used to monitor the procedure. This technique can be especially helpful in cases with challenging ultrasonic windows and ultimately to avoid the requirement of transthoracic or transesophageal echocardiography. Previously, only Pedone et al¹¹ suggested the value of ICE to guide this procedure. In 9 patients, these investigators selected the target septal branch on the basis of the risk-area visualized using ICE after injection of a contrast agent. No further experience with this technique has been reported.

Some additional features of the present case deserve especial comments: First, our findings emphasize the limited effect of alcohol injection in areas different from those generating the maximal gradient.^4–8 In fact, in our patient, the anatomical distribution of septal branches precluded a more precise location of the alcohol at the target myocardial segment. As a result, our patient experienced some symptomatic improvement and a reduction in the severity of mitral regurgitation, but a significant gradient persisted at follow up at the left ventricular outflow tract. Second, in some cases, the procedure of septal ablation may be technically demanding and/or associated with complications.⁸ The occurrence of major coronary dissections has been reported, but remains exceedingly rare.⁸ The mild, type-A, left main coronary dissection induced in our patient was not associated with any clinical implication. However, special care should be taken to prevent this problem when excessive movement of the tip of the guiding catheter is noticed during the procedure. The possibility that the “thin-walled” coronary arteries of children and adolescents might provide a higher-risk substrate for this complication remains speculative, but deserves further attention.

Third, in patients with HOCM, some investigators have suggested the possibility of using stents to treat coronary segments with severe milking. In fact,this angiographic finding appears to be a marker of bad prognosis in children and adolescents.¹² However, we believe that great caution is required before considering this alternative therapeutic strategy.^13–15 Coronary stenting should only be considered as the last-resort option in patients with severe, objective and refractory ischemia, since this technique could lead to the appearance not of restenosis, but rather to the development of a new stenosis in a previously healthy coronary segment.^14,15

Conclusions. Our findings suggest that ICE constitutes a useful tool to guide procedures of alcohol septal ablation in patients with HOCM. This technique requires expertise and is not free of procedure-related complications and suboptimal results.

References

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