Reversible Atrioventricular Block Research Articles

Reversible atrioventricular block after atrial septal defect closure with a Gore Cardioform Septal Occluder

Reversible atrioventricular block after atrial septal defect closure with a Gore Cardioform Septal Occluder

Complete AV Block and Torsades de Pointes in a Case of Primary Cardiac T-Cell Lymphoma.

Primary cardiac lymphoma is very rare, and the most common electrocardiographic finding in this condition is complete atrioventricular block. After electrolytic, metabolic, ischemic, infectious, and traumatic etiologies have been excluded, primary cardiac lymphoma should be consided as a possible cause of reversible atrioventricular block. Most patients with primary cardiac lymphoma are immunocompromised and have disease with a B-cell etiology. This is the first case report of a primary cardiac T-cell lymphoma with complete atrioventricular block and torsades de pointes in an immunocompetent patient who was successfully treated using chemotherapy. Atrioventricular block; T-cell lymphoma; Torsades de pointes.

Atrioventricular block in patients with thyroid dysfunction: Prognosis after treatment with hormone supplementation or antithyroid medication

BackgroundHypothyroidism is a reversible cause of atrioventricular (AV) block. Few reports have described reversible AV block caused by hyperthyroidism. However, it is unknown whether patients with AV block are expected to have a benign course after the initiation of appropriate therapy for thyroid dysfunction. MethodsThe study group consisted of patients with II or III degree AV block and bradyarrhythmia (≤40bpm) excluding patients with myocardial infarction, electrolyte abnormalities, digitalis toxicity, and vasovagal syncope. Thyroid dysfunction is diagnosed when thyroid stimulating hormone and thyroxine levels are not in defined normal ranges. AV block was determined by surface electrocardiogram (ECG). The cause and effect relation between AV block and thyroid dysfunction was evaluated. ResultsOf 668 patients, 29 (4.3%) had hypothyroidism (19 overt) and 21 (3.1%) had hyperthyroidism (8 overt). The most frequent ECG finding was complete AV block (27 of 50 patients). Ten patients had bradyarrhythmia and 13 had second-degree AV block. Euthyroid state was achieved in 10 hypothyroidic (34%) and in 7 hyperthyroidic patients (33%) with hormone replacement and antithyroid therapy, respectively, during the follow-up period (≤21 days). Thyroid dysfunction was found to be not related with AV block in 40 patients (80%). However, in 4 of 10 patients with AV block related to thyroid dysfunction the resolution of AV block occurred after the placement of pacemaker (>21 days). Overall, 44 of 50 (88%) patients with AV block in association with thyroid dysfunction were implanted with a permanent pacemaker. Of 6 patients who did not receive a pacemaker, 2 had complete AV block and 4 had bradyarrythmia. ConclusionAV block associated with thyroid dysfunction needs great attention regardless of type of the thyroid disease. Patients with II and/or III degree AV block in the setting of thyroid dysfunction almost always need permanent pacemaker insertion even after normalization of thyroid status.

Reversibility of Atrioventricular Block According to Coronary Artery Disease: Results of a Retrospective Study

Background and ObjectivesThe causal relationship of clinically-significant atrioventricular block (AVB) and coronary artery disease (CAD) is uncertain. We investigated whether CAD is related to irreversible AVB that requires treatment with a permanent pacemaker.Subjects and MethodsWe included 188 consecutive patients with new-onset AVB considering pacemaker, who had undergone invasive or noninvasive coronary evaluation. Patients were divided into one of 2 groups: irreversible AVB who underwent implantation of permanent pacemaker {irreversible block (IB) group, n=173} or reversible AVB {reversible block (RB) group, n=15}.ResultsIn IB group, significant CAD was observed in 44 patients (25.4%) and there were 2 (1.2%) patients with acute myocardial infarction (AMI). In RB group, 14 patients (93.3%) had CAD (p<0.001) and 13 patients (86.7%) presented with AMI (p<0.001). On the aspect of CAD type and reversibility of AVB, 13/15 (86.7%) patients of AMI, 0/2 (0%) of unstable angina, and 1/41 (2.4%) of stable angina had reversible AVB.ConclusionAVB in patients with AMI is usually reversible. Therefore, permanent pacemaker implantation should be delayed in cases of AMI. AVB in patients with CAD other than AMI is usually irreversible.

Transcatheter Cryoablation Part I: Preclinical Experience

The concept of cooling to treat medical disorders dates back to the ancient Egyptian Edwin Smith Papyrus on surgical trauma, written between 3000 and 2500 B.C. Hypothermic therapy was recommended for abscesses that were “oily, like fluid under thy hand, [which] produce some clamminess of the surface.”1 Modern forms of cryothermal tissue ablation have been used surgically for decades in numerous organ systems and for various pathologies. Unlike heat that destroys cells by coagulation and tissue necrosis with potential for thrombus formation and aneurysmal dilatation, cryoablation involves a distinct pathophysiological process. As such, it carries a unique safety and efficacy profile. While not novel as an energy modality, harnessing cryoenergy into a steerable transcatheter format represents a more recent landmark in the history of arrhythmia therapy. In Part I of this two-part series, we will focus on the body of knowledge underlying the development of a transcatheter cryoablation system. Pertinent features related to biophysics and mechanisms of cryothermal tissue injury will be highlighted, key historical developments considered, and experience gained from cryosurgery with hand-held probes summarized. Preclinical studies with transcatheter cryoablation will be detailed, setting the framework for human applications. Part II of this series will review the current state of knowledge regarding clinical experience with transcatheter cryoablation.

Reversible atrioventricular block associated with closure of atrial septal defects using the Amplatzer Device: Suda K, Raboisson M, Piette E, Dahdah NS, Miro J. J Am Coll Cardiol 2004;43:1677–82

Reversible atrioventricular block associated with closure of atrial septal defects using the Amplatzer Device: Suda K, Raboisson M, Piette E, Dahdah NS, Miro J. J Am Coll Cardiol 2004;43:1677–82

Reversible atrioventricular block associated with closure of atrial septal defects using the amplatzer device

ObjectivesWe sought to determine the incidence, nature, and predisposing factors of atrioventricular block (AVB) associated with closure of atrial septal defects (ASDs) using the Amplatzer septal occluder (ASO). BackgroundIn our institution, 162 patients underwent ASD closure using ASO between December 1997 and December 2001. This includes small children with large defects. MethodsElectrocardiographic tracings during ASO implantation and at follow-up visits were reviewed. Anatomic characteristics and device size were assessed as potential risk factors for AVB. ResultsTen patients (6.2%) presented with new-onset (n = 9) or aggravation of preexisting (n = 1) AVB. Atrioventricular block occurred during the procedure (n = 3) or was first noted one day to one week later (n = 7). Patients had first-degree (n = 4), second-degree Wenckebach (n = 4), or third-degree (n = 2) AVB, with no symptoms or hemodynamic compromise. First-degree AVB persisted in two patients at 12 and 33 months of follow-up, whereas most recovered normal AV conduction within one (n = 7) or six months (n = 1). A larger shunt (Qp/Qs ratio 2.8 ± 0.9 vs. 2.1 ± 0.8, p < 0.01) and device size (24 ± 5 vs. 19 ± 6 mm, p < 0.01) were the only determinant factors for AVB. A device size ≥19 mm was used in 90% (9 of 10) of patients who developed AVB, as compared with 49% of those without AVB (p < 0.02). ConclusionsClosure of ASDs using the large ASO can be associated with the development of AV block and mandate a closer follow-up. In our series, however, all AVBs resolved or improved spontaneously, with no recurrence at mid-term follow-up.

Microwave ablation of the atrioventricular junction in open-chest dogs.

The use of microwave energy for ablation of the atrioventricular (AV) junction was examined in open-chest dogs. Using a specially designed microwave catheter and a 2450 MHz generator, microwave energy was delivered to the AV junction according to one of two protocols. In protocol 1, increasing amounts of energy were delivered until irreversible AV block occurred. In protocol 2, only two applications of energy were used, one at low energy and the other at an energy found to be high enough to cause irreversible AV block. Each dog received between one and six applications of microwave energy. The amount of energy delivered per application ranged from 25.6 to 311.4 J. No AV block was seen at 59.4 +/- 28.3 J. Reversible AV block was seen with an energy of 120.6 +/- 58 J. Irreversible AV block was seen at 188.1 +/- 75.9 J. Irreversible AV block could be achieved in each animal. There was no difference in the energy required to cause irreversible AV block between the two protocols. The tissue temperature measured near the tip of the microwave catheter was correlated with both the amount of energy delivered and the extent of AV block caused. Histologic examination demonstrated coagulation necrosis of the conduction system. Microwave energy is a feasible alternative energy source for myocardial ablation. Since tissue damage is due exclusively to heating and the resulting rise in temperature can be measured, microwave energy may have advantages over currently existing energy sources in terms of both titrating delivered energy and monitoring the extent of tissue destruction.

The response of atrioventricular junctional tissue to temperature.

To determine the optimal temperature for catheter heat mapping without damaging cardiac tissue, we studied the electrophysiologic and histologic responses of the atrioventricular (AV) conduction system exposed to a specific range of temperatures. In 18 closed-chest dogs, an electrode catheter with a thermistor, tip was positioned transvenously at the AV junction. Radiofrequency current (RFC) was applied in incremental temperature steps until transient 2nd-degree AV block was induced. Catheter tip temperature (CTT) was measured at each step. RFC was immediately discontinued when AV block occurred. AV conduction was evaluated before and 4 weeks after the procedure. Acute transient 2nd-degree AV block was induced in 45 applications, during which the average CTT was 48.7 +/- 2.7 degrees C. In another 40 applications in which 2nd degree AV block was not induced, the average CTT was significantly lower [46.3 +/- 2.5 degrees C] (p < 0.001). Eleven of 16 dogs showed acute 2nd-degree AV block, but had normal AV conduction at 4 weeks (Group A). In the other 5 dogs, 1st-degree AV block was seen at 4 weeks (Group B). The lowest CTTs in Groups A and B were 45 and 49 degrees C, respectively. Histologic findings in 2 dogs from Group A revealed that 10-15% (by area) of the AV node was fibrotic. These findings suggest that the induction of fully reversible AV block can be achieved by titration of RFC, during the application of RFC to the AV junction. In conclusion, RF energy was used to produce a tip temperature of between 45 degrees C and 49 degrees C, which induced reversible and significant interruption of conduction of in tissue in the AV junction, and presumably also in target sites in clinical RF ablation.

Cryosurgical modification of the atrioventricular node: A closed heart approach in the dog

Intraoperative modification of the atrioventricular (AV) node to prolong refractoriness could be an alternative to His bundle ablation in patients with refractory supraventricular arrhythmias. It was postulated that a cryosurgical lesion at the posterior interatrial septum in the closed heart could achieve this. An electrophysiologic study was performed in anesthetized dogs. The AV fat pad was mobilized to expose the posteroseptal region. A cryoprobe cooled to 0 to -10 degrees C was moved in the exposed region until reversible AV block indicated proximity of the AV node. The probe was then cooled to -70 degrees C for 30 seconds. Four weeks later, five dogs had a favorable result with a mean prolongation of Wenckebach cycle length of 45 +/- 7% (p less than 0.05). Two dogs had complete heart block. Decreased (one dog) or increased (one dog) duration of freezing resulted in no change and complete heart block, respectively. Histologic examination verified partial damage to the AV node with preservation of the His bundle. Thus, controlled cryoinjury to modify AV node function is feasible in the closed heart; preservation of AV conduction provides an advantage over His bundle ablation.

Reversible Atrioventricular Block in Myxedema

Disturbances in atrioventricular conduction with myxedema have been described. The present study describes three such cases with varying degrees of atrioventricular block, which reverted to normal sinus rhythm following thyroid hormone replacement There is a strong likelihood that myxedema and reversible atrioventricular block following therapy represent a significant association. In view of the rarity of pharmacologic reversibility in atrioventricular block, the need to screen patients for myxedema is stressed. Microscopic examination of the cardiac muscle in one case revealed the presence of PAS positive material in a perinuclear distribution in the cytoplasm of a myocardial fiber. Disturbances in atrioventricular conduction with myxedema have been described. The present study describes three such cases with varying degrees of atrioventricular block, which reverted to normal sinus rhythm following thyroid hormone replacement There is a strong likelihood that myxedema and reversible atrioventricular block following therapy represent a significant association. In view of the rarity of pharmacologic reversibility in atrioventricular block, the need to screen patients for myxedema is stressed. Microscopic examination of the cardiac muscle in one case revealed the presence of PAS positive material in a perinuclear distribution in the cytoplasm of a myocardial fiber.