Rapid atrial stimulation in the treatment of supraventricular tachycardia

Problems of sensing tachyarrhythmias by an antitachycardia pacemaker (Symbios 7008)

Atrial burst pacing is an effective method of terminating supraventricular tachycardia. In the patient presented in this report, a Symbios 7008 pacemaker (Medtronic Inc., Minneapolis, MN, USA) was implanted for two reasons: (1) severe AV conduction defect (AH, 230 msec; HV, 150 msec) and bifascicular block following anterior myocardial infarction; and (2) paroxysmal atrial flutter. The conduction defect ruled out programming other than atrial burst in DDD mode. Activation of burst pacing required appropriate programming of the "tachycardia detection window" on the basis of the cycle length of the flutter waves. In the case reviewed, episodes of atrial flutter with variable cycle lengths of 230 to 280 msec necessitated reprogramming of the AV interval, the refractory period, and the upper rate interval. The use of an antitachycardia device in automatic mode may be limited by variations in tachycardia cycle length.

Limitations to activation of the antitachycardia burst pacing function of the Symbios 7008 pacemaker in the universal (DDD) mode

The Symbios 7008 antitachycardia pacemaker was implanted in five patients for control of supraventricular tachycardia. Shortly after implantation in the first two patients, it was noted that the burst pacing sequence was not automatically activated by tachycardia when the pacemaker was in the DDD mode. Data from these two and the subsequent three patients were evaluated to explain this observation. The problem was primarily related to the operation of the device during the postventricular atrial refractory period. In all patients, the atrial electrogram encroached upon the programmed postventricular atrial refractory period because VA conduction during SVT was less than the lowest programmable interval (155 ms). Atrial events occurring during this interval will not trigger the tachycardia termination sequence. In all five patients, the size of the atrial electrogram decreased substantially (48 +/- 10%; mean +/- SD) during supraventricular tachycardia compared to sinus rhythm. In at least two of the five patients, decreased atrial size during supraventricular tachycardia may also have resulted in intermittent failure of atrial sensing during tachycardia, even at the most sensitive setting (0.6 mV). The latter may remain a problem even if the technical fault in SVT detection in the DDD mode were corrected. Two related problems were noted in the DDD mode: ventricular events during rapid SVT do not reset the low rate interval, resulting in random low rate pacing; and, automatic prolongation of atrial refractory period by two successive ventricular events without an intervening atrial sensed event compounds problems of atrial sensing. All of these problems were easily circumvented in all patients by noninvasive reprogramming to the DVI mode in which supraventricular tachycardia detection is based on ventricular sensing. These findings have implications for the future design of such devices.

Indications for and complications of temporary transvenous cardiac pacing

A prospective survey was conducted of the indications for and complications of 153 temporary transvenous cardiac pacing lead insertions in 148 patients. Pacing for bradyarrhythmias or potential bradyarrhythmias (Group I) accounted for 105 insertions, wide complex tachycardia (Group II) 17, and narrow complex tachycardia (Group III) 31 pacing electrode insertions respectively. The infraclavicular subclavian vein approach was used in 73%. The median insertion time was 20 minutes. Group I: 77% were undertaken because of severe symptoms. On 64 occasions (61%) the patient had complete heart block or ventricular asystole. Group II: The lead was inserted to treat and often assist in the diagnosis of the wide complex tachycardia. Ventricular 'burst' pacing reverted ventricular tachycardia in 13 (76%). Group III: Rapid atrial 'burst' pacing was used to treat supraventricular tachyarrhythmias (paroxysmal supraventricular tachycardia and atrial flutter) resistant to medical therapy. Pacing was successful in reverting 28 (90%). A complication occurred in 27 (18%) of 153 lead insertions, 11 (7%) were serious. No complication resulted in the death of a patient. Temporary transvenous pacing is safe and effective for the treatment of bradyarrhythmias and certain tachyarrhythmias.

Cardiac pacing in intensive care

Cardiac pacing techniques and equipment have developed dramatically in recent years. Bradycardias and tachycardias may be effectively treated by pacing. Bradyarrhythmias: It is generally accepted that pacing is indicated for a sustained symptomatic bradycardia. Prophylactic pacing for 'high-risk' bundle branch block in acute myocardial infarction is more controversial. A new era in cardiology has been introduced with the advent of 'physiological pacing', i.e. pacing of the heart with the maintenance of atrioventricular synchrony and varying the heart rate according to the body's metabolic leads. Modern pacing systems, which allow the atria and ventricles to contract in sequence, improve cardiac haemodynamics, result in subjective improvement and increase exercise tolerance. There are, however, pacemaker-associated and pacemaker-mediated tachyarrhythmias. Further advances in technology should overcome these problems. Tachyarrhythmias: Intracardiac electrocardiograms are often useful in the diagnosis of tachyarrhythmias, especially wide complex tachycardias. Rapid pacing of the atria in certain supraventricular tachycardias or of the ventricle in ventricular tachycardia is an alternative to cardioversion in many instances. This form of treatment is usually utilised in conjunction with drug therapy.

Patient-activated transvenous cardiac stimulation for the treatment of supraventricular and ventricular tachycardia

Recurrent, drug-refractory sustained tachycardias present a difficult management problem. After invasive electrophysiologic study and extensive antiarrhythmic drug testing, a permanent transvenous lead system and radiofrequency stimulator that required patient activation for burst pacing were implanted in eight patients with refractory ventricular tachycardia. In a follow-up period of 2 to 28.5 months (mean 12) each patient has successfully terminated multiple episodes of recurrent tachycardia without complication. This therapeutic approach has allowed a reduction in antiarrhythmic drug dosage and adverse effects, has obviated the need for frequent hospital admissions resulting from recurrent tachycardia, and has met with excellent patient acceptance.

Overdrive and programmed atrial electrostimulation in the study of the electrogenetic mechanism of atrial flutter in man

The response of atrial flutter (AF) to programmed atrial stimulation (PAS) (13 cases) and overdrive atrial pacing (OAP) ws studied in a total of 18 patients. During PAS the return cycle was equal to the basic cycle of AF in six patients, shorter in one patient, and slightly longer in six; it was never compensatory. ATrial flutter terminated in two patients by PAS and by OAP in three. In 4 patients, PAS resulted in an acceleration of the AF rate, followed by spontaneous interruption within 2 seconds. In the remaining patients, the stimulation either converted the AF into an uncommon type of AF (two patients) or into atrial fibrillation that was followed by spontaneous return to sinus rhythm. In two patients it was possible to reproduce the AF with PAS; in one of the patients another type of AF was induced. Some of the data observed suggest a re-entry circuit as the electrogenetic mechanism responsible for AF in man.

Autodecremental pacing--a microprocessor based modality for the termination of paroxysmal tachycardias

Five patients aged between 27 and 48 years were referred for investigation of recurrent paroxysmal tachycardias. Electrophysiological studies revealed concealed ventriculoatrial accessory pathways in two patients, possible atrionodal pathways in two patients and dual intranodal pathways in one patient. During electrophysiological study, particular attention was paid to methods of terminating tachycardia by pacing techniques including single or double atrial and ventricular extrastimuli, atrial or ventricular underdrive, atrial overdrive pacing, and in two patients, rapid ventricular pacing. 'Autodecremental' atrial pacing was employed in all five patients and autodecremental ventricular pacing in two patients. This system is controlled by a microprocessor interfaced with a stimulator. When tachycardia of a cycle length less than 375 ms is sensed the system initiates pacing sequences. The initial stimulus is introduced at an interval less than the tachycardia cycle determined by a preset decremental value D. Each subsequent pacing interval is reduced by the value of D resulting in a gradual acceleration of pacing. The total duration of pacing is limited by the value of the pacing period (P). The final pacing rate is determined by P but cannot exceed 275 bpm (cycle length of 218 ms). Both P and D are operator programmable variables. Tachycardias of a cycle length less than 218 ms do not activate the pacemaker. The postpacing sensing deadtime of the system is set at 50 ms. In three patients, double atrial extrastimuli or atrial overdrive initiated atrial flutter or fibrillation. Autodecremental atrial pacing was successful in converting tachycardia to sinus rhythm in all five patients without initiation of other tachyarrhythmias. Autodecremental ventricular pacing was successful in one of the two patients in which it was used. This new modality of pacing has several theoretical advantages over conventional methods: the decremental mode may avoid stimulation in the vulnerable period and minimizes the risk of initiating other tachyarrhythmias; gradual acceleration of pacing over a short period results in stimulation at different phases of the tachycardia cycle length; and the operator variables D and P provide a flexible system which may be adjusted to suit a particular patient and tachycardia. The development of a fully implantable programmable system is made attractive by the simplicity and adaptability of this technique.

The response of regular re-entrant supraventricular tachycardia to right heart stimulation

The study was designed to assess the effect of various forms of right atrial or ventricular stimulation on the termination of re-entrant "supraventricular" tachycardias. Standard electrophysiological techniques were used in 81 patients to study 86 stable tachycardias. All tachycardias were initiated by single or double atrial or ventricular premature stimuli or incremental atrial pacing. Eight groups of tachycardia circuit were defined in terms of the anterograde and retrograde pathways. Termination of each tachycardia was studied by atrial underdrive, ventricular underdrive, rapid atrial stimulation and single or double atrial and ventricular premature extrastimuli. Intranodal re-entrant tachycardias formed 33% of the total and WPW tachycardias as a whole formed 55% of the total number of arrhythmias. The remainder were comprised of atrial tachycardia (5%), tachycardias in association with a partial AV nodal bypass (3%) and pre-excited tachycardias (5%). A single atrial extrastimulus was most effective where the circuit involved the right atrium. Atrial underdrive was consistently less successful than a single atrial extrastimulus in all groups. Rapid atrial pacing was effective in all groups, but caused transient atrial flutter or fibrillation in a proportion of each group except one. Ventricular underdrive stimulation was most effective in those groups where the right ventricle was involved in the circuit, but tended to be less effective than programmed single or double ventricular extrastimuli. Pacemakers designed to deliver appropriately timed single or double extrastimuli may offer an important alternative to other pacing modalities.

Hemodynamic effects of various modes of cardiac pacing after operation for idiopathic hypertrophic subaortic stenosis

The hemodynamic effects of varying heart rate and pacing site were studied in 6 patients with idiopathic hypertrophic subaortic stenosis following operative relief of outflow obstruction. Ventricular pacing (117 beats per minute) resulted in a 26% decrease in cardiac output (p less than 0.02), a 54% increase in pulmonary capillary wedge pressure (p less than 0.03), and a 23% decrease in mean blood pressure (p less than 0.05), compared with normal sinus rhythm (88 beats per minute). Slow atrial pacing (112 beats per minute) did not significantly alter any hemodynamic variable compared with normal sinus rhythm. Rapid atrial pacing (143 beats per minute) produced a similar degree of hemodynamic impairment as ventricular pacing. This study demonstrates that ventricular pacing at heart rates commonly used clinically and rapid atrial rates result in a significant fall in cardiac output. Preservation of atrial systole at heart rates that allow adequate diastolic ventricular filling of a hypertrophied, noncompliant ventricle is stressed. In addition, atrial electrodes are useful to record atrial electrograms or induce rapid atrial stimulation to treat supraventricular tachyarrhythmias.

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.

Continuous rapid atrial pacing to control recurrent or sustained supraventricular tachycardias following open heart surgery

A technique is described to control recurrent or sustained supraventricular tachycardia associated with rapid ventricular rates following open heart surgery. The technique utilizes a pair of temporarily implanted atrial epicardial wire electrodes to pace the heart. In one group of patients with recurrent atrial flutter and 2:1 A-V conduction, continuous rapid atrial pacing at 450 beats/min produced and sustained atrial fibrillation. The ventricular response rate immediately slowed when compared to that during atrial flutter, and if further slowing was required, it was easily accomplished by the administration of digitalis. Another group of patients with different arrhythmias (recurrent paroxysmal atrial tachycardia, sustained ectopic atrial tachycardia, or sinus rhythm with premature atrial beats which precipitated runs of atrial fibrillation) was treated with continuous rapid atrial pacing to produce 2:1 A-V block. In all instances, the continuous rapid atrial pacing suppressed the supraventricular tachycardia and maintained the ventricular response rate in a therapeutically desirable range. It was demonstrated that the technique is safe, effective, and reliable.

Patient-initiated rapid atrial pacing to manage supraventricular tachycardia

Patient-controlled rapid atrial pacing was used to manage 12 cases of recurrent supraventricular tachycardia refractory to drug therapy. The pacing system consists of an implanted receiver-lead system and an external patient-activated transmitter. In each case, brief periods (5 to 20 seconds) of rapid atrial pacing were effective in terminating the supraventricular tachycardia and resulted in a return to normal sinus rhythm. In three patients, occasional transient episodes of atrial flutter or atrial fibrillation preceded a spontaneous return to normal sinus rhythm. The pacing system was removed in one patient 13 months postoperatively because of persistent pericarditis; one patient died of an unrelated cerebral hemorrhage 13 months postoperatively. Successful management of supraventricular tachycardia has been maintained in the 10 remaining patients for 15 to 36 months (average 26.4). In more than 6,000 patient applications of rapid atrial pacing, there has been only one failure to convert the tachycardia. Successful application of permanent rapid atrial pacing requires (1) prescreening of patients with temporary external rapid atrial pacing to verify susceptibility to conversion of supraventricular tachycardia and absence of anomalous conduction pathways that may permit conduction of rapid pacing rates to the ventricles, and (2) assessment of the patient's ability to use the transmitter properly.

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.

The triple pulse generator: Clinical evaluation of a new multipurpose external pulse generator

This report describes our experience with a new, versatile battery operated, multi-purpose pulse generator especially designed for the electrophysiological investigation and treatment of cardiac arrhythmias in man. The unit was constructed according to our specifications and has been clinically in 75 patients over a period of 18 months. We have found the triple pulse pacemaker safe, reliable and functioning precisely according to specifications both clinically and when repeatedly checked with a storage oscilloscope.