Atrial pacing: its diagnostic and therapeutic applications

Evaluation of the Appropriateness of Pacemaker Mode Selection in Bradycardia Pacing:

Although guidelines for selection of the appropriate pacing mode have been published, little data is available on how closely these are followed in the clinical setting. All 738 patients (men 412, women 326; age 73.4 +/- 0.46 years; range 19-101 years) who underwent pacemaker implantation from 1996 to 2000 were reviewed to determine if the appropriate mode was selected based on the ACC/AHA guidelines with the data collected prospectively. Demographic, investigational, and implantation data including the presence of sinus disease and/or atrioventricular block, diagnosis, indication for pacing, ACC/AHA class indication for device therapy, recommended ACC/AHA mode, implanted mode, and reason for not using the recommended mode were entered into an SPSS data base. Of 738 patients, 708 were cross-tabulated for a match to the guidelines of which 358 (50.6%) had a mode selected that did not conform. The reasons were advanced physical disability (16%), physician choice without identifiable reason (21%), rate modulation selected without identifiable indication (16%), DDD implanted instead of VDD (25%), advanced age (9%), rare need for pacing (6%), a need for specific device features (5%), and unstable stimulation thresholds or difficult venous access (2%). In the treatment of bradyarrhythmias, deviation from the ACC/AHA indicated mode occurred in a substantial proportion of pacing system implantations. However, in many, the deviation appeared appropriate considering the patient's clinical status. Nevertheless, in a smaller proportion of patients the deviation appeared inappropriate requiring rectification. The two outstanding categories were: (1) elderly denied a dual chamber system with no clinical explanation and (2) selection of rate-modulated devices without any indication of chronotropic incompetence.

Response of atrial flutter to overdrive atrial pacing and intravenous disopyramide phosphate, singly and in combination

Ten patients who suffered spontaneous paroxysms of atrial flutter were investigated by electrophysiological techniques. Two had overt Wolff-Parkinson-White syndrome; three Lown-Ganong-Levine syndrome; and one a concealed accessory atrioventricular connection. Atrial flutter was initiated, at study, by right atrial pacing and electrograms from the right atrium and coronary sinus were observed for at least five minutes to ensure stable flutter in both atria. Atrial flutter was terminated by 2.5 s or 5 s bursts of atrial pacing at rates 10, 50, or 100 beats/min faster than the intrinsic flutter rate in only two patients. Atrial flutter, which was reinitiated in two patients, was then treated with intravenous disopyramide phosphate, 2 mg/kg body weight, infused over five minutes. In all 10 patients the atrial rate slowed from a mean of 310 +/- 39 beats/min to 217 +/- 27 beats/min and atrial flutter terminated in one case. Though the mean ventricular rate fell from 161 +/- 52 beats/min to 156 +/- 45 beats/min the atrioventricular conduction ratio fell from 2.17 +/- 0.86 to 1.55 +/- 0.59 and four patients were left with symptomatically significant increases of ventricular rate. In seven of nine patients overdrive atrial pacing, repeated after disopryamide, resulted in the conversion of atrial flutter to sinus rhythm. In this study, overdrive atrial pacing and intravenous disopyramide, singly and in combination, terminated atrial flutter in nine of the 10 patients and it is suggested that this method may provide an effective alternative to direct current cardioversion.

Overdrive pacing for supraventricular tachycardia: a review of theoretical implications and therapeutic techniques

Rapid atrial pacing for treatment of supraventricular arrhythmias has been demonstrated to be safe and effective. Virtually any supraventricular tachycardia with the exception of atrial fibrillation, Type II atrial flutter, and probably sinus tachycardia can be treated successfully with pacing techniques. The recognition of the advantages of cardiac pacing over drug therapy or DC cardioversion has resulted in its widespread use, especially after open-heart surgery. Although the response to overdrive pacing may not reliably identify the underlying mechanism of supraventricular tachycardia, the response of the arrhythmia to pacing (i.e., whether it is interruptable or noninterruptable), is most useful in the approach to management of the individual patient.

Atrial pacing for cardioversion of atrial flutter in digitalized patients

To test the safety and reliability of atrial pacing as a conversion technique in patients with atrial flutter who are receiving digitalis therapy, atrial pacing conversion was attempted for 49 episodes of atrial flutter in 32 consecutive patients. All patients except one were receiving digitalis. To control ventricular rates most patients had received larger than usual therapeutic doses of digitalis glycoside before pacing. Fourteen of the 25 patients whose serum levels were measured had glycoside concentrations greater than 2 ng/ml. Before atrial pacing the mean atrial and ventricular rates were, respectively, 290 +/- 20.6 and 134 +/- 27.9/min (mean +/- standard deviation). Successful rhythm conversion was achieved on 48 occasions (98%) in 31 patients. One patient required transthoracic direct current synchronized countershock cardioversion. With atrial pacing, the atrial flutter rhythm reverted immediately to sinus mechanism in 23 instances, and there were 25 episodes of atrial fibrillation. Among those who experienced atrial fibrillation, the rhythm spontaneously reverted to sinus mechanism within 24 hours on 14 occasions; on 11 occasions; the rhythm reverted to atrial flutter and repeat pacing was required. Sinus mechanism was eventually established in all 31 patients.

Coronary sinus pacing clinical follow-up

Coronary sinus pacing is a safe and effective means of pacing from the atrium. In 66 patients with an average follow-up of 14 months, there was a 14% failure rate. There were transient problems in 14% which were subsequently corrected. There was a 6% death rate which was not pacemaker related. Successful atrial pacing with thresholds up to 6.0 mA is feasible. Atrial pacing was successful in 18 of 19 patients with varying degrees of atrioventricular block. Our experience with a new electrode has been very satisfactory.

Sinus node function and conduction system after complete repair of tetralogy of Fallot

Twenty-three children underwent electrophysiological studies during routine postoperative catheterization two months to five years after complete correction of tetralogy of Fallot. The aim of the study was to investigate the whole conduction system, including sinus node function, suing His bundle recordings and atrial pacing. H-V intervals were normal at rest and with pacing in twenty-two patients, including four patients with evidence of bifascicular block on the surface ECG. One patient with cardiomegaly and evidence of diffuse myocardial damage had a prolonged H-V interval but did not develop a block at this level during pacing A-H interval was slightly prolonged in four patients and normal in all others. The threshold of pacing-induced atrioventricular block ranged from 75 to 240/min and was somewhat age dependent (r = -0.55). Two patients fell below the 95% confidence limit of this regression and are considered abnormal. One returned to normal after intravenous injectionof atropine. Corrected sinus node recovery time ranged from 60 to 2000 msec. Three patients had values above 500 msec which are considered abnormal. These patients had other minor signs of sinus node dysfunction, i.e., episodes of sino-atrial block at rest or intermittent sinus bradycardia. Thus, while the His Purkinje system performed satisfactorily in all patients, sinus node dysfunctional and A-V node dysfunction were demonstrated in a few patients after correction of tetralogy of Fallot.

Refractory reentrant atrial tachycardia. Successful treatment with a permanent radio frequency triggered atrial pacemaker

This 68 year old man had recurrent episodes of paroxysmal atrial tachycardia, probably due to chronic pericarditis, persisting over a 7 year period. These episodes were resistant to all conventional medical therapy and at times produced ischemic chest pain. There was no evidence of Wolff-Parkinson-White syndrome either on the standard electrocardiogram or on the His bundle electrogram performed with atrial pacing. Rapid atrial pacing at a rate of 200/min was found to promptly terminate the tachycardia and restore normal sinus rhythm. Because of the refractoriness of the patient's tachycardia, in addition to the presence of ischemic chest pain during these episodes, a permanent radio frequency triggered atrial pacemaker was inserted which enables him to initiate rapid atrial pacing by pressing an external control. The patient has been maintained on antiarrhythmic medications in an attempt to decrease the frequency of these episodes; during an 8 month follow-up period, he has done well with approximately one episode of tachycardia each month requiring radio frequency atrial pacing for termination.

Therapeutic uses of permanent pervenous atrial pacemakers: A review

The available techniques for permanent pervenous atrial pacing have been reviewed with particular emphasis on the coronary vein approach. The major therapeutic uses for permanent atrial pacing include sinus node dysfunction, recurrent ventricular tachyarrhythmias, and intractable supraventricular tachycardias. Special types of atrial pacing involve the use of bifocal atrioventricular sequential pacing, paired atrial pacing, and rapid atrial pacing generators. The potential problems associated with the coronary vein atrial pacing method are discussed.

The pathophysiology of tachycardia-dependent paroxysmal atrioventricular block after acute myocardial ischemia. Experimental and clinical observations

The pathophysiology of paroxysmal A-V block (PAVB) was studied in 20 anesthetized dogs after ligation of the anterior septal artery. Simultaneous recording of leads II and aV R , as well as intracardiac recordings from the His bundle (Hb) and both bundle branches, were monitored. In 18 of 20 experiments, PAVB was localized in the Hb. In all experiments, PAVB occurred subsequent to Mobitz type II A-V block. In eight experiments, PAVB occurred spontaneously during sinus rhythm and was preceded by a period of Wenckebach periodicity superimposed upon a 2:1 A-V block. Vagal-induced slowing of the sinus rate resulted in immediate resumption of 1:1 A-V conduction. In 18 experiments, PAVB was induced by atrial pacing at a critical heart rate in each case (180-300 beats/min). Evidence is presented that A-V conduction was consistently blocked below a critical H-H interval. Slowing the pacing rate, termination of pacinig or increasing the pacing rate until physiological A-V nodal block occurred, all could result in a longer H-H interval and immediate resumption of A-V conduction. When the critical heart rate for PAVB was maintained, a slow idioventricular escape rhythm occurred.

Five patients who developed PAVB after acute myocardial ischemia are also reported providing the clinical counterpart for the experimental observations. In all five cases, PAVB occurred on acceleration of the sinoatrial rate (105-140 beats/min) which was spontaneous in two and induced by drugs given for varied therapeutic indications in three (isoprenaline in two and atropine sulfate in one). In all five, PAVB was associated with Mobitz type II and/or 2:1 A-V block. These experimental and clinical observations suggest that PAVB after acute myocardial ischemia appears to be due to a tachycardia-dependent repetitive concealed conduction in the ischemic His-Purkinje system, probably mainly in the Hb. The clinical observations point out potential consequences of a rapid atrial rate in patients with acute myrocarcial ischemia and type II A-V block.

Use of atropine for higher right atrial pacing rates. 'Maximal' pacing for diagnosis of coronary artery disease

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