Septal Ablation with Radiofrequency Catheters Guided by Echocardiography for Treatment of Patients with Obstructive Hypertrophic Cardiomyopathy: Initial Experience

Abstract

Background: Hypertrophic cardiomyopathy (HCM) can cause obstruction in the left ventricular outflow tract (LVOT), and be responsible for the onset of limiting symptoms, such as tiredness. When such symptoms are refractory to pharmacological treatment, interventionist alternative therapies can be useful, such as septal ablation through the infusion of alcohol in the coronary artery or through myectomy. Recently, the use of a radiofrequency (RF) catheter for endocardial septal ablation guided by electroanatomic mapping has proven to be efficient, despite the high incidence of complete atrioventricular block. An alternative would be the application of RF at the beginning point of the septal gradient guided by the transesophageal echocardiography (TEE). The echocardiography is an imaging method with high accuracy to determine septal anatomy.

Objective: To assess the long term effect of septal ablation for the relief of ventricular-arterial gradient, using TEE to help place the catheter in the area of larger septal obstruction. Besides, to assess the effects of ablation on the functional class and echocardiographic parameters.

Methods: Twelve asymptomatic patients, with LVOT obstruction, refractory to pharmacological therapy, underwent endocardial septal ablation with 8mm-tip catheters, whose placement was oriented in the region of larger obstruction, assisted by the TEE. Temperature-controlled and staggered RF applications were performed. After each application, the gradient was reassessed and a new application was performed according to the clinical criterion. The effects of RF applications were assessed both for the gradient at rest and for that provoked by the Valsalva maneuver, and considering the gradient. The differences were significant when p-value was lower than or equal to 0.05.

Results: It was possible to observe that the mean reduction of the maximum gradients was from 96.8±34.7 mmHg to 62.7±25.4 mmHg three months after the procedure (p=0.0036). After one year, the mean of maximum gradient was 36.1±23.8 mmHg (p=0.0001). The procedure was well tolerated, without records of complete atrioventricular block nor severe complications.

Conclusion: The TEE-guided septal ablation was efficient and safe, and the results were maintained during the clinical follow-up period. It is a reasonable option for the interventionist treatment of LVOT obstruction in HCM.

Figura 1. – Fluorsocopia em projeção obliqua anterior direita a 30 o, na qual se observa a sonda do ETE(seta azul, alem dos cateteres na região do feixe de His(seta verde) e o cateter de RF(terapêutico) em vermelho.

Figura 2. – Fluxograma de seleção e acompanhamento dos pacientes.

Figura 3. – Ecocardiografia transesofágica perioperatória, na qual podem ser observados o septo interventricular refringente (seta vermelha) e o cateter terapêutico de radiofrequência (RF) que, após ultrapassar a válvula aórtica, é impactado no septo (seta azul). Esta região é definida pelo ecocardiografista como sendo a de maior gradiente. Nesse ponto, a RF é aplicada e, se reduzido o gradiente em pelo menos 25%, novas aplicações são repetidas ao redor da primeira aplicação, estendendo-se a área de lesão.

Figura 4. – Variação dos gradientes máximos em repouso pré-procedimento, após três meses e após 12 meses, para cada paciente. Observe a redução significativa do gradiente após a ablação, resultado que se manteve até os 12 meses de observação.

Figura 5. – Variação dos gradientes máximos pré-procedimento provocados pela manobra de Valsalva após três meses e após 12 meses, para cada paciente. Do mesmo modo, como observado no gradiente repouso, houve redução significativa do gradiente após ablação, resultado que se manteve até os 12 meses de observação.

Figura 6. – Variação de classe funcional pré e ao término do seguimento de um ano.

Figure 1. – Fluoroscopy in a 30º right anterior oblique position, in which it is possible to observe the TEE probe (blue arrow), besides the catheters in the His axis region (green arrow) and the RF catheter (therapeutic). para Fluoroscopy in a 30º right anterior oblique position, in which it is possible to observe the TEE probe (blue arrow), besides the catheters in the His axis region (green arrow) and the RF catheter (therapeutic) - red arrow

Figure 2. – Flowchart showing patient selection and follow-up.

Figure 3. – Perioperative transesophageal echocardiography, which shows the refringent interventricular septum (red arrow) and the radiofrequency (RF) therapeutic catheter, which, after surpassing the aortic valve, is impacted on the septum (blue arrow). This region is defined by the echocardiography professional as the one with the highest gradient. At this point, RF is applied and, if the gradient is reduced in at least 25%, new applications are repeated around the first application, thus extending the lesion area.

Figure 4. – Variation of maximum gradients at rest and pre-procedure, after three and 12 months, for each patient. It is possible to observe the significant reduction of the gradient after ablation, and this result was maintained until the 12 months of observation.

Figure 5. – Variation of maximum pre-procedure gradients provoked by the Valsalva maneuver after three and 12 months, for each patient. Likewise, as observed in the at rest gradient, there was significant reduction of the gradient after ablation, and this result was maintained until the 12 months of observation.

Figure 6. – Variation of functional classification before and after the one-year follow-up.