[Catheter cryoablation for the treatment of supraventricular arrhythmias]. / La cryoablation endocardiaque percutanée dans le traitement des arythmies supraventriculaires.

Catheter ablation is a radical treatment for various severe and drug-refractory arrhythmias. Radiofrequency is the reference energy for ablation, but has some limitations. Cryoenergy gradually freezes myocardial tissue, allowing the consequences to be predicted before inducing the lesion. Furthermore, the lesions are better-circumscribed and less thrombogenic than those induced by radiofrequency. Twenty-two patients (12 women) aged from 20 to 79 years with drug-refractory supraventricular arrhythmias underwent cryoablation. The ablation catheter was cooled by nitrous oxide expansion. The electrophysiological properties of the tissue are reversibly lost at a temperature of -30 degrees C, allowing cryomapping. When the appropriate target has been located, the temperature is reduced to -70 degrees C. The cryoablation is painless. The procedure was initially successful in all 12 patients with atrionodal reentrant tachycardias, usually after one or two applications. However, during the 8-month follow-up period, slower, transient tachycardia recurred in 3 patients. We observed no cases of atrioventricular (AV) block, a possible complication of radiofrequency. Cryoablation was successful and safe in two patients with an accessory pathway (Kent). In eight patients with atrial fibrillation and uncontrolled ventricular tachycardia, cryoablation was used with the aim of slowing nodal conduction. Initial success was obtained in 7 cases (3 modulations and 4 complete AV blocks) but only persisted in four cases, suggesting that more applications should be used or different sites targeted. The efficacy and safety of cryoablation make it an attractive option for the ablation of small substrates close to the nodo-Hisian tissue (atrionodal reentries and accessory pathways). New criteria must be developed to define long-term success of cryoablation of the AV node, which is successful in the acute setting.

Prophylactic pacemaker implantation in familial amyloid polyneuropathy.

BACKGROUND: Familial amyloid polyneuropathy (FAP) is an autosomic dominant disease with a high rate of conduction disorders and increased risk of sudden death. Prophylactic cardiac pacing may be considered in asymptomatic patients with FAP. However, the potential benefits are unknown. OBJECTIVE: To document conduction disorders in a large series of FAP and the incidence of high-degree atrioventricular (AV) block in patients with prophylactic pacemaker (PM). METHODS: From January 1999 to January 2010, 262 patients with FAP were retrospectively evaluated. Prophylactic PM was implanted in patients with His-ventricular interval ≥ 70 ms, His-ventricular interval >55 ms associated with a fascicular block, a first-degree AV block, or a Wenckebach anterograde point ≤ 100 beats/min. The spontaneous AV conduction was then analyzed by temporarily inhibiting the PM. RESULTS: As compared with patients with prophylactic PM (n = 100) and patients implanted given a class I/IIa indication (n = 18), the patients who did not require PM (n = 144) were younger and displayed less severe cardiac involvement. Follow-up after prophylactic PM implantation was analyzed in 95 of the 100 patients over 45 ± 35 months, and a high-degree AV block was documented in 24 of the 95 patients (25%). The risk of high-degree AV block was higher in patients with first-degree AV block or Wenckebach anterograde point ≤ 100 beats/min (hazard ratio 3.5; 95% confidence interval 1.2-10) while microvoltage on surface electrocardiogram reduced the risk (hazard ratio 0.2; 95% confidence interval 0.1-0.7). CONCLUSION: In FAP with conduction disorders, prophylactic PM implantation prevented major cardiac events in 25% of the patients over a 45-month mean follow-up. It is suggested that prophylactic PM implantation prevented symptomatic bradycardia in these patients.

Circadian rhythm of blood pressure reflects the severity of cardiac impairment in familial amyloid polyneuropathy.

BACKGROUND: Cardiac amyloidosis due to familial amyloid polyneuropathy (FAP) includes restrictive cardiomyopathy, thickened cardiac walls, conduction disorders and cardiac denervation. Impaired blood pressure variability has been documented in FAP related to the Val30Met mutation. AIMS: To document blood pressure variability in FAP patients with various mutation types and its relationship to the severity of cardiac involvement. METHODS: Blood pressure variability was analysed in 49 consecutive FAP patients and was compared with a matched control population. Cardiac evaluation included echocardiography, right heart catheterization, electrophysiological study, Holter electrocardiogram and metaiodobenzylguanidine (MIBG) scintigraphy. RESULTS: A non-dipping pattern was found in 80% of FAP patients and in 35% of control patients (P<0.0001); this was due to a significantly lower diurnal blood pressure in FAP patients (FAP group, 113 ± 21 mmHg; control group, 124 ± 8 mmHg; P<0.0001), whereas nocturnal blood pressures were similar. Among FAP patients, a non-dipping pattern was significantly associated with haemodynamic involvement, cardiac thickening or conduction disorders. These associations did not depend on the average blood pressure levels. Impaired blood pressure variability was more frequent and more pronounced in patients with multiple criteria for severe cardiac amyloidosis. CONCLUSION: Low blood pressure variability is common in cardiac amyloidosis due to FAP. A non-dipping pattern was more frequently observed in FAP patients with haemodynamic impairment, cardiac thickening or conduction disorders. It is suggested that impairment of circadian rhythm of blood pressure reflects the severity of cardiac amyloidosis due to FAP.