Supraventricular Tachycardia Induced by Swallowing: A Case Report and Review of the Literature

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71974/1/j.1540-8159.1987.tb05933.x.pd

An Analysis of Post-Pacing R-R Intervals During Atrial Fibrillation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74691/1/j.1540-8159.1986.tb04496.x.pd

Prevention of recurrent atrial fibrillation with chronic dual-site right atrial pacing

AbstractObjectives. We investigated 1) the feasibility, safety and efficacy of multisite right atrial pacing for prevention of atrial fibrillation (AF); and 2) the ability of atrial pacing in single- and dual-site modes to increase arrhythmia-free intervals in patients with drug-refractory AF.Background. We recently developed and applied a novel technique of dual-site right atrial pacing in an unselected group of consecutive patients with AF requiring demand pacing. A prospective crossover study design was used to evaluate single- and dual-site right atrial pacing modes.Methods. The frequency of AF during the 3 months before pacemaker implantation was analyzed. Consecutive consenting patients underwent insertion of two atrial leads and one ventricular lead with a DDDR pulse generator. Patients were placed in a dual-site pacing mode for the first 3 months and subsequently mode switched to single site pacing for 3 months. Mode switching was repeated at 6-month intervals thereafter.Results. Atrial pacing resulted in a marked decline in AF recurrences (p < 0.001). During dual-site pacing with an optimal drug regimen, there was no AF recurrence in any patient compared with five recurrences in 12 patients during single-site pacing (p = 0.03). The mean (±SD) arrhythmia-free interval before pacing (14 ± 14 days) was prolonged with dual- (89 ± 7 days, p < 0.0001) and single-site pacing (76 ± 27 days, p < 0.0001). Symptomatic AF episodes showed a declining trend during dual- and single-site pacing compared with those during the preimplantation period (p = 0.10). Mean antiarrhythmic drug use for all classes declined from 4 ± 1.9 drugs before implantation to 1.5 ± 0.5 (p < 0.01) drugs after implantation. Twelve (80%) of 15 patients remained in atrial paced rhythm at 13 ± 3 months.Conclusions. We conclude that multisite right atrial pacing is feasible, effective and safe for long-term application. Atrial pacing significantly prolongs arrhythmia-free intervals in patients with drug-refractory paroxysmal AF. Dual-site right atrial pacing may offer additional benefits and should be considered either as the primary mode or in patients unresponsive to single-site pacing

Immediate reproducibility of clinical and nonclinical forms of induced ventricular tachycardia

This prospective study assessed the immediate reproducibility of clinical and nonclinical forms of ventricular tachycardia (VT) induced by programmed ventricular stimulation. Twenty-three clinical VTs were unimorphic and previously documented and 22 nonclinical VTs (17 polymorphic and 5 unimorphic) were induced in patients with either no documented or suspected history of VT, or documented VT that had a configuration different from that of the induced VT. The stimulation protocol included 1 to 3 ventricular extrastimuli, 2 drive cycle lengths, and 2 right ventricular stimulation sites. Each VT was induced on the first attempt, then the stimulation protocol was repeated twice in the drug-free state. After the first VT induction, 21 of 23 clinical VTs (91%) and 17 of 22 nonclinical VTs (77%) were reinduced on the second attempt. After 2 VT inductions, 21 of 21 clinical VTs (100%) and 15 of 17 nonclinical VTs (88%) were reinduced on the third attempt. The reinduction rates of the clinical and nonclinical VTs were not significantly different. Among the clinical VTs, the reproducibility of the induction technique was 81% after 1 induction and 88% after 2 inductions with the same technique. These results imply that (1) acute drug testing can be reliably performed after 2 inductions but not 1 induction of clinical VT; (2) reproducibility is not helpful in determining whether an induced VT is clinical or nonclinical; and (3) changes in induction technique during drug testing should be interpreted with caution because changes may occur in the absence of drugs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26088/1/0000164.pd

Effects of high stimulation current on the induction of ventricular tachycardia

Programmed stimulation at 2 right ventricular sites with 1 to 3 extrastimuli was performed at current strengths of twice diastolic threshold (1.0 +/- 0.2 mA, mean +/- standard deviation) and 10 mA in 41 patients undergoing an electrophysiologic study because of sustained ventricular tachycardia (VT) (11 patients), nonsustained VT (19 patients) or unexplained syncope (11 patients). In 26 patients, VT was not induced by programmed stimulation at twice diastolic threshold. Programmed stimulation at 10 mA induced VT or ventricular fibrillation in 16 of these 26 patients (62%). In 4 of 16 patients, the coupling intervals of the extrastimuli that induced VT/ventricular fibrillation at 10 mA were all equal to or longer than the shortest coupling intervals resulting in ventricular capture at twice diastolic threshold. Fifteen patients had inducible VT at twice diastolic threshold. Programmed stimulation at 10 mA induced a similar VT in 12 of these patients, but resulted in no VT induction in 3 of 15 patients (20%), despite ventricular capture at the same coupling intervals that had induced VT at twice diastolic threshold.This study shows that programmed stimulation at a high current strength may either facilitate or prevent induction of VT. Facilitation of VT induction usually is attributable to a shortening of ventricular refractoriness and the ability of extrastimuli at 10 mA to capture the ventricle at shorter coupling intervals than possible at twice diastolic threshold. However, in 25% of cases, the facilitation of VT induction by 10-mA stimuli is not explained by a shortening of ventricular refractoriness. In these cases, and in the patients in whom 10-mA stimuli prevent the induction of VT that was inducible at twice diastolic threshold, the effects of high current strength appear to be mediated through some other mechanism. Other possible mechanisms include an effect on temporal dispersion of refractoriness or on the pattern or extent of ventricular activation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25627/1/0000177.pd

Clinical significance of ventricular fibrillation-flutter induced by ventricular programmed stimulation

Two hundred twenty-four patients underwent ventricular programmed stimulation (VPS) without prior documentation of the clinical occurrence of sustained ventricular tachycardia (VT) or ventricular fibrillation-flutter (VF). Indications for VPS were: palpitations or nonsustained VT during ambulatory monitoring (85 patients), syncope or presyncope (137 patients), and a family history of sudden death (two patients). Sustained VF requiring transthoracic defibrillation was initiated by VPS in 18 patients (8.0%). Four patients were treated for inducible VF with antiarrhythmic agents directed by electropharmacologic testing; five patients were treated empirically; nine patients received no therapy. No patient has had a cardiac arrest or sudden death during a follow-up period of 25.2 +/- 13.8 months (mean +/- standard deviation). VF was initiated by two ventricular extrastimuli in three patients and by three extrastimuli in 15 patients. The incidence of VF was similar in patients with and without previous symptoms (8.8% vs 6.9%) or heart disease (7.1% vs 9.6%). It was significantly higher when VPS at three ventricular sites with a current of 5 mA (pulse width 2 msec) was compared to programmed stimulation at two ventricular sites with a current twice diastolic threshold (pulse width 2 msec) (15.2% vs 3.0%, p &lt; 0.05). VF initiated by VPS in patients without prior VT or VF appears to be a nonspecific finding. Antiarrhythmic therapy for VF may not be necessary in these patients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25695/1/0000249.pd

The hemodynamic effects of ventricular pacing with and without atrioventricular synchrony in patients with normal and diminished left ventricular function

The relative hemodynamic effects of heart rate, inotropic state, and atrioventricular (AV) synchrony during ventricular pacing were evaluated in 10 patients with normal left ventricular ejection fraction (LVEF) (0.66 +/- 0.07, mean S.D.) and in eight patients with a diminished LVEF (0.34 +/- 0.18). Hemodynamics were measured at AV intervals of 130, 0, and -130 msec during ventricular pacing at a baseline rate that was 10 pulses/min greater than the resting heart rate, at 130 pulses/min alone, and at 130 pulses/min during continuous intravenous infusion of dobutamine. During baseline ventricular pacing and during ventricular pacing at 130 pulses/min with and without dobutamine, both groups of patients had a significant decrease in cardiac index, stroke volume index, and stroke work index when the AV pacing interval was decreased from 130 to 0 msec. The observed decrease in these three hemodynamic variables was similar when patients with diminished LVEF were compared to patients with normal LVEF. No further significant decrease in cardiac index, stroke volume index, and stroke work index occurred in either group when the AV interval was changed from 0 to -130 msec during baseline ventricular pacing or during ventricular pacing at 130 with and without dobutamine. Beneficial hemodynamic effects occur during ventricular pacing when AV synchrony is maintained at resting heart rates and during increases in heart rate and inotropic state in patients with normal and diminished LVEF.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26988/1/0000555.pd

1008-14 Radiofrequency Catheter Ablation of Left-sided Accessory Pathways: Selection of Coronary Sinus as the Primary Approach

We employed the coronary sinus (CS) for radiofrequency catheter ablation either as a primary technique or as a secondary approach after failed endocardial attempts in 12 pts (mean age 40±20 yrs) with 14 accessory pathways (AP): 9 left paraseptal, 4 left posterolateral, 1 left anterolateral. AP to local atrial (AP/A) and ventricular (AP/V) electrogram amplitude ratios were calculated. CS angiograms were obtained in 9 pts. Results: AP potentials were recorded from the CS in all pts. All APs were successfully ablated using either CS ablation alone or combined with LV endocardial ablation. Catheter ablation within the CS eliminated conduction in 10 of 14 (71.4%) APs (Group 1) with the median of 7 (range 3 to 14) radiofrequency pulses and mean duration of 18±5s at mean power of 22±3W; 5 of these 10 APs were ablated from the CS as a primary method, and the other 5 APs were ablated from the CS after the failure of prior endocardial ablation. In remaining 4 APs (Group 2) the primary CS ablation failed and pathways were ablated with a subsequent endocardial approach. In Groups 1&amp;2, AP/A ratio was 1±0.5 &amp; 0.55 ±0.1 (p&lt;0.05), and AP/V ratio was 1.2±0.6 &amp;0.4 ±0.3 (p &lt;0.05), respectively. In Group 1,9/10 successful ablations had an AP/A andlor AP/V ratios ≥1, whereas in Group 2 none of the CS recordings had an electrogram ratio ≥1. In all 5 Group 1 pts failing endocardial ablation, an AP potential was not recorded at the, endocardial site. 5 of 7 successfully ablated left paraseptal APs were adjoining the middle cardiac vein or a CS anomaly. CS perforation or thrombosis was not observed. During followup of 10 ±7 mos there was no recurrence of sustained supraventricular tachycardia in any pt.Conclusions(1) The CS can be used for both mapping as well as safe and effective ablation of left-sided APs with radiofrequency power outputs upto 30W. (2) It can be utilized as a primary ablation approach for APs with AP/A or AP/V ratios ≥1. (3) These findings are most commonly seen in left paraseptal APs in proximity to the middle cardiac vein or a venous anomaly. (4) Endocardial ablation can be reserved for left-sided APs with electrogram ratios &lt;1