P696Incidence of sinus node dysfunction with cancer chemotherapy: a systematic review of literature

Background

Introduction of newer classes of chemotherapeutic agents has led to improved survival in many cancers, often at the cost of increased side effects. With the advent of cardio-oncology, there has been growing focus on cardiac side effects of chemotherapy like cardiomyopathy, QT prolongation, VT and AF. However, data on cancer chemotherapy related sinus node dysfunction (SND) is limited.

Objective

To assess the incidence of chemotherapy related SND through a systematic review of available literature.

Methods

We performed a systematic review of PUBMED database for studies reporting SND (including sinus bradycardia, sinus pauses, sinoatrial exit blocks or asystole) with use of chemotherapeutic agents. Weighted average incidence of SND was calculated from studies. Case reports were reported independently.

Results

2012 articles were reviewed of which 38 were eligible for data extraction. Incidence of SND varied significantly between drug classes. However, specific drugs were associated with increased incidence of SND like anthracyclines (Epirubicin 8.3%), antimetabolites (5 Fluorouracil 20%), tyrosine kinase inhibitors (crizotinib 43%), antimicrotubule agents (paclitaxel 29%) and angiogenesis inhibitors (Thalidomide 22%). The weighted average incidence is shown in table.

Drug type Drug Type of cancers No. of studies Total No. Weighted average of incidence of sinus arrhythmias No. of case reports Anthracyclines Epirubicin Breast, Hodgkin's disease 1 24 8.3% 1 Idarubicin CML – – – 1 Unclassified anthracyclines Ewing sarcoma 2 370 4.31% – Antimetabolites 5 Fluorouracil Esophageal, gastric, colon, rectal 1 5 20% 1 Capecitabine Rectal cancer – – – 1 Methotrexate Osteosarcoma – – – 1 Cytarabine AML – – – 1 Antimicrotubule agent Paclitaxel Ovarian cancer 2 4505 29.36% – Kinase inhibitors Crizotinib Lung 2 1095 43% 4 Alectinib Lung 1 225 5% – Ibrutinib Mantle cell lymphoma – – – 1 Monoclonal antibodies Infliximab Ulcerative colitis – – – 1 Angiogenesis inhibitors Thalidomide Multiple myeloma 4 83 21.62% 2 Endostar Metastatic colorectal and gastric 1 23 13% – Selective estrogen modulators Tamoxifene Extracranial meningioma – – – 1 Antiandrogen Abiraterone Prostate cancer 1 17 6% – Other drugs Crisnatol mesylate Advanced solid tumors 1 43 2.3% – Mitoxantrone AML – – – 1 Combination drugs Bevacizumab +Vorinostat Malignant Glioma 1 40 3% – All-trans-retinoic acid+idarubicin AML – – – 2 Tivantinib+Erlotinib Advanced solid malignancies 1 32 23.1% – Paclitaxel+Carboplatin+Bevacizumab Lung – – – 1 Paclitaxel+Carboplatin Ovarian 1 79 2.9% – Daunorubicin+Amsacrine AML – – – 1 CHOP Diffuse large B cell lymphoma – – – 1

Conclusion

There is cumulative evidence of increased incidence of SND with certain chemotherapeutics. In pre-existing SND, certain drugs and combinations must be avoided and alternative agents, should be considered. Future studies are needed to evaluate the role of remote cardiac monitoring and permanent pacing in specific situations where no safer alternatives exist.

Radiofrequency catheter ablation of atriofascicular and nodoventricular Mahaim tracts

BACKGROUND

Several mechanisms have been proposed to explain the pathogenesis of tachycardia in patients with Mahaim tracts. The tachycardia may involve antegrade conduction over an atriofascicular pathway with decremental properties or a nodofascicular pathway.

METHODS AND RESULTS

We report six patients with recurrent episodes of preexcited tachycardia with findings consistent with "Mahaim tract" conduction. All patients exhibited decremental antegrade preexcited conduction with atrial pacing and a preexcited tachycardia with initial activation of the proximal right bundle branch. In four patients (group 1), atrial premature complexes (APCs) induced at the tricuspid annulus just after the inscription of the septal atrial electrogram and during left bundle branch block preexcited tachycardia advanced the next preexcited ventricular complex. In these patients, discrete Mahaim potentials were inscribed over the right anterolateral or lateral tricuspid annulus. Two patients (group 2) had evidence of dual atrioventricular nodal conduction. APCs during left bundle branch block tachycardia just after inscription of the septal atrial electrogram failed to advance the next ventricular complex with similar preexcited morphology, and no Mahaim potentials could be recorded from the tricuspid annulus. In group 1 patients, application of radiofrequency energy to sites recording the Mahaim potentials resulted in tachycardia cure. For patients in group 2, selective slow atrioventricular nodal pathway ablation in the midseptal region resulted in complete ablation of both the slow atrioventricular nodal pathway and Mahaim conduction in two patients.

CONCLUSIONS

Mahaim tachycardia can be due to atriofascicular pathways, which may be ablated over the right tricuspid annulus, or to septal pathways, which may arise from the slow atrioventricular nodal pathway in patients with dual atrioventricular nodal physiology. In the latter circumstance, successful ablation is achieved by placing the lesion in the midseptal region.

Curative percutaneous catheter ablation using radiofrequency energy for accessory pathways in all locations: results in 100 consecutive patients

Patients with accessory pathway-mediated supraventricular tachycardia have typically been treated with drugs or surgery. Although catheter ablation using high voltage direct current shocks has been used to treat patients with drug-refractory supraventricular tachycardia, there are associated disadvantages, including damage due to barotrauma as well as the need for general anesthesia. Recently, transcatheter radiofrequency energy has evolved as an alternative to direct current shock or surgery to ablate accessory pathways. Percutaneous catheter ablation of 109 accessory pathways with use of radiofrequency energy was attempted in 100 consecutive patients. Patient age ranged from 3 to 67 years. The patients had been treated for recurrent tachycardia with a mean of 2.7 +/- 0.2 antiarrhythmic agents that either proved ineffective or caused unacceptable side effects. In seven patients previous attempts at accessory pathway ablation with use of direct current shock had been unsuccessful. Forty-five (41%) of the pathways were left free wall, 43 (40%) were septal and 21 (19%) were right free wall. Eighty-nine (89%) of the 100 patients had successful radiofrequency ablation at the time of hospital discharge. In all but 12 patients the ablation was accomplished in a single session. Complications attributable to the procedure, but not to the ablation itself, occurred in four patients (4%). No patient developed atrioventricular block or other cardiac arrhythmias. Over a mean follow-up period of 10 months, nine patients had some return of accessory pathway conduction; a repeat ablation procedure was successful in all five patients in whom it was attempted. It is concluded that a catheter ablation procedure using radiofrequency energy can be performed on accessory pathways in all locations. The procedure is effective and safer, less costly and more convenient than cardiac surgery and can be considered as an alternative to lifelong medical therapy in any patient with symptomatic accessory pathway-mediated tachycardia.

Catheter modification of the atrioventricular junction with radiofrequency energy for control of atrioventricular nodal reentry tachycardia

BACKGROUND

The utility of transcatheter application of radiofrequency energy to eliminate atrioventricular nodal reentrant tachycardia (AVNRT) was investigated.

METHODS AND RESULTS

Thirty-nine patients (mean age, 53 +/- 20 years; range 14-86 years) with medically refractory AVNRT underwent perinodal ablation with radiofrequency energy. A custom-designed 6F catheter with a large (3-mm-long) distal electrode and interelectrode pacing of 2 mm was used in the majority of cases. The catheter used for ablation was initially positioned across the tricuspid anulus to obtain the largest His bundle electrogram, then withdrawn to obtain the largest atrial:ventricular electrogram ratio, with a small His bundle electrogram (less than or equal to 100 microV). Each application of radiofrequency energy (350-550 kHz, 16.2 +/- 5.2 W) was stopped after 60 seconds or if PR prolongation or an impedance rise was noted. The endpoints of the procedure were persistent modification of atrioventricular nodal conduction (either first-degree atrioventricular block or impairment of ventriculoatrial conduction) and noninducibility of AVNRT before and during isoproterenol administration. Radiofrequency energy was applied a mean of 6.8 +/- 3.5 times per session. After a mean follow-up of 8 +/- 3.0 months, 32 of the 39 patients (82%) have been free of AVNRT, and did not have high grade AV block. Three patients (8%) developed complete atrioventricular block and had pacemakers implanted. Two patients had unsuccessful initial procedures, and two patients had initially successful ablations but had recurrences of tachycardia 4-6 weeks later. Elimination of AVNRT appeared to be due to effects on the retrograde fast pathway in most patients.

CONCLUSIONS

Radiofrequency ablation of the perinodal right atrium appears to be safe and effective for treatment of typical AVNRT:

Ablation of the atrioventricular junction with radiofrequency energy using a new electrode catheter

Percutaneous catheter ablation using radiofrequency energy can be used to interrupt atrioventricular (AV) conduction in patients with supraventricular tachycardia refractory to drugs. Results of radiofrequency ablation of the AV junction using a custom-designed catheter with a large, 3-mm-long distal electrode, 2-mm interelectrode spacing, and a shaft with increased torsional rigidity were compared with those using a standard quadripolar electrode catheter (Bard EP). An electrocoagulator (Microvasive Bicap 4005) supplied unmodulated radiofrequency current at 550 kHz, which was applied between the distal electrode of the ablation catheter and a large skin electrode. With use of the modified catheter, 12 of 13 patients (92%) had persistent complete AV block induced with 7 +/- 5 applications of 18 +/- 6 W of radiofrequency power. In contrast, complete AV block was produced in only 9 of 18 (50%) historical control patients treated with the standard catheter, despite a similar number of applications (7 +/- 5) and power output (16 +/- 4 W). A rise in impedance, due to desiccation of tissue and coagulum formation, occurred earlier (28 +/- 18 vs 52 +/- 24 seconds, p less than 0.001) and more frequently (54 vs 40% of applications, p = 0.047) in patients treated with the standard catheter than in patients treated with the modified catheter. The use of a catheter designed to increase the surface area of electrode-tissue contact allows more radiofrequency energy to be delivered before a rise in impedance occurs and appears to increase the effectiveness of radiofrequency ablation of the AV junction.

Clinical significance of radionuclide angiographically-determined abnormalities following acute blunt chest trauma

Abnormalities of right and left ventricular ejection fraction and segmental wall motion may be detected by radionuclide angiography (RNA) following blunt chest trauma. Of 111 patients with blunt chest trauma who were admitted to a large regional shock trauma center and underwent combined first-pass and equilibrium gated RNA, abnormalities were present in 40 (36%). These abnormalities were confined to the right ventricle in 33 patients. There was a positive association between RNA abnormalities and the presence of right bundle branch block (10 of 40, p less than 0.05) and a negative association between RNA abnormalities and the finding of rib fractures (6 of 40, p less than 0.05). The in-hospital death rate of these patients was low (3 of 40 patients with an abnormal RNA and 2 of 71 patients with a normal RNA). Follow-up RNA was performed at 10 +/- 4 days in 26 of the 40 patients with initially abnormal scans, and 22 (85%) of the 26 had reverted to normal. Thus although RNA abnormalities appear common following blunt chest trauma, among patients who survive for more than 24 hours and who undergo subsequent RNA, the complication rate is low despite an abnormal scan. We conclude that routine RNA adds little to clinical management following acute blunt chest trauma.

Pindolol therapy for bradycardia/tachycardia syndrome

Bradycardia/tachycardia syndrome (BTS) is notoriously refractory to drug therapy. Three patients with BTS unresponsive to digitalis or digitalis plus verapamil (ventricular response continued intermittently rapid despite prolonged pauses) were prescribed oral pindolol, a beta blocker with intrinsic sympathomimetic activity. The ventricular rate was well-controlled in all and no adverse effects were seen. Pindolol may be of value in selected patients with BTS.