Case report: Delayed detection of ventricular tachycardia due to intradevice interactions by implantable atrio-ventricular pacer/cardioverter defibrillator.

Current generations of implantable cardioverter defibrillators are capable of providing sophisticated dual chamber atrioventricular and rate-responsive pacing therapies, and even cardiac resynchronization therapy. Appropriate programming of the devices is necessary for them to perform all such sophisticated tasks. In this report, we describe a case where detection of ventricular tachycardia was delayed due to intradevice interactions between the pacemaker and defibrillator components of the device.

Decremental ramp atrial extrastimuli pacing protocol for the induction of atrioventricular nodal re-entrant tachycardia and other supraventricular tachycardias.

AIM: The primary aim of this study was to evaluate the utility of decremental ramp atrial extrastimuli pacing protocol (PRTCL) for induction of atrioventricular nodal re-entrant tachycardia (AVNRT), and other supraventricular tachycardias (SVTs), compared to standard (STD) methods. METHODS: The study cohort of 121 patients (age 57.51 +/- 14.02 years) who presented with documented SVTs and/or symptoms of palpitations and dizziness, and underwent invasive electrophysiological evaluation was divided into Group I (AVNRT, n = 42) and Group II (Control, n = 79). The PRTCL involved a train of six atrial extrastimuli, delivered in a decremental ramp fashion. The STD methods included continuous burst and rapid incremental pacing up to atrioventricular (AV) block cycle length, and single and occasionally double atrial extrastimuli. Prolongation in the Atrio-Hisian (Delta-AH) intervals achieved by both methods were compared, as were induction frequencies. RESULTS: In Group I, three categories of responses--(1) induction of AVNRT, (2) induction of echo beats only, and (3) none--were observed in 29 (69%), 11 (26%), and 2 (5%) patients with the PRTCL, when compared with 14 (33%), 16 (38%), and 12 (29%) patients with STD methods in the baseline state without the use of pharmacological agents. The Delta-AH intervals for each of these three categories were larger using PRTCL versus STD methods; 293.3 +/- 95.2 ms versus 192.9 +/- 61.4 ms (P < 0.005), 308.6 +/- 68.5 ms versus 189. 9 +/- 64.9 ms (P < 0.0005), and 203.0 +/- 86.3 ms versus 145.8 +/- 58.9 ms (P = NS), respectively. In Group II, in one patient with dual AV nodal physiology but no clinical tachycardia, the PRTCL induced nonsustained (12 beats) AVNRT. Additionally, in this group, both PRTCL and STD methods induced atrial tachycardia in two patients and orthodromic AV re-entrant tachycardia in one patient. CONCLUSION: Decremental ramp atrial extrastimuli pacing PRTCL demonstrates a superior response for induction of typical AVNRT as compared to STD techniques. Because of easy and reliable induction of AVNRT and echo beats by the PRTCL, we recommend it as a method to increase the likelihood of induction of AVNRT. For induction of other SVTs, the PRTCL and the STD methods are comparable.

Prediction of the recurrence of atrial fibrillation after cardioversion in the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study.

BACKGROUND: The early recurrence of atrial fibrillation (AF) after cardioversion and the need for frequent cardioversions to maintain sinus rhythm are important clinical features of AF management. METHODS: We evaluated patients in the AFFIRM study whose qualifying episode of AF lasted > or = 48 hours and was terminated by cardioversion. Clinical, electrocardiographic, and echocardiographic risk factors associated with AF recurrence within 2 months of cardioversion and > or = 2 cardioversions during the first year were identified using multivariate analysis in 1293 eligible patients. RESULTS: The risk factors for the recurrence of AF within 2 months of cardioversion were no coronary artery disease and an electrocardiographic lead II P-wave duration of > 135 milliseconds. In the subset of patients not taking antiarrhythmic drug therapy, the multivariate risk factors were no coronary artery disease, second or greater episode of AF, left ventricular ejection fraction < 0.50, and mitral valve thickening. Significant risk factors for the need for > 2 cardioversions in the first year in patients taking antiarrhythmic medication were left atrial diameter > 4.5 cm and mitral valve thickening. The overall sensitivity and specificity of these parameters for recurrence and repeated cardioversion are low. CONCLUSION: There are several risk factors for difficulty maintaining sinus rhythm after cardioversion of persistent AF. The clinical predictive value of these factors is low, and they probably should not be used to justify withholding rhythm control efforts in patients who might benefit from sinus rhythm.

Comparison of management patterns and clinical outcomes in patients with atrial fibrillation in Canada and the United States (from the analysis of the Atrial Fibrillation Follow-up Investigation of Rhythm Management [AFFIRM] database).

Little is known about differences in practice patterns or outcomes in the management of patients who have atrial fibrillation in Canada compared with those in the United States (US). We evaluated the effect that the country of enrollment may have on the management patterns and clinical outcomes in patients who participated in the AFFIRM study. Three thousand four hundred patients came from the US and 660 from Canada. In the US, patients were more likely to have a history of coronary artery disease (39% vs 35%, p = 0.03), hypertension (72% vs 67%, p = 0.01), or congestive heart failure (24% vs 18%, p = 0.0002). More US participants were <65 years of age (25% vs 19%, p = 0.003). Although at randomization the use of warfarin was comparable, during follow-up Canadians were more likely to be treated with warfarin and to be therapeutically anticoagulated. Mortality rate at 5 years was higher in US patients (24% vs 16%, p = 0.001), and the composite end point (death, disabling stroke, major bleeding, cardiac arrest, or anoxic encephalopathy) was also higher in US patients (30% vs 22%, p = 0.0005). Even after adjusting for known differences in baseline characteristics, the risk of death was lower in Canada (hazard ratio 0.70, p = 0.02). In conclusion, in the AFFIRM study, US subjects were more likely to have preexisting cardiovascular diseases despite being younger (<65 years old) than those in Canada. Effective warfarin therapy was more commonly employed in Canada. After correcting for the known differences in baseline characteristics, Canadian patients who had atrial fibrillation had a lower mortality risk.

Electroanatomical mapping and radiofrequency catheter ablation of atrial tachycardia originating from the recipient heart with recipient-to-donor atrio-atrial conduction after orthotopic heart transplantation.

Atrial tachycardias resulting from recipient-to-donor atrio-atrial conduction after orthotopic heart transplantation are difficult to treat. We present two patients in whom atrial tachycardia originating in the recipient heart were successfully treated by radiofrequency ablation guided by electroanatomical CARTO mapping system. These cases illustrate that such atrial tachycardia are curable by radiofrequency ablation. Electroanatomical CARTO mapping is useful in identifying the site of origin of the tachycardia and the atrio-atrial conduction sites.

Usefulness of pindolol for treatment of neurocardiogenic syncope.

This study evaluated the efficacy of pindolol, a noncardioselective beta blocker with intrinsic sympathetic activity, on neurocardiogenic syncope using a head-up tilt-table test in 66 patients. Pindolol was equally effective in men and women and the 2 age groups (>60 and <60 years) of the study cohort. The earliest benefit was seen

Pathophysiology and management of neurocardiogenic syncope.

OBJECTIVE: To discuss the physiologic mechanisms underlying neurocardiogenic syncope in the context of several different management strategies. PATHOPHYSIOLOGY: Neurocardiogenic syncope or the "common faint" is variously called neurally mediated hypotension, vasovagal syncope, or vasodepressor syncope. It is the most common type of syncope. The pathophysiology of neurocardiogenic syncope is complex and not completely elucidated. Individuals susceptible to neurocardiogenic syncope are unable to maintain the adaptive neurocardiovascular responses to upright posture for prolonged periods. These patients tend to have a modest reduction in central blood volume, which is aggravated by upright posture. It is often noted in individuals receiving sympathetic blocking agents and vasodilator drugs for hypertension, elderly patients receiving tranquilizers, patients with anemia, and individuals with tran- sient reductions in blood volume such as those that occur after a brisk diuresis or blood donation. The classic syncopal episode often is preceded by a constellation of prodromal symptoms several seconds before the event that may include nausea, headache, diaphoresis, dizziness, chest pain, palpitations, dyspnea, and paresthesia. MANAGEMENT: Head-up tilt testing has become the diagnostic study of choice for the identification of patients with neurocardiogenic syncope. Therapeutic options include general measures such as volume expansion; pharmacologic approaches such as beta-adrenergic receptor blockade, anticholinergic agents, selective serotonin reuptake inhibitors, methylxanthines, and alpha agonists; and invasive methods such as placement of a dual-chamber cardiac pacemaker.