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Pacing termination of spontaneous ventricular tachycardia in the coronary care unit
International Journal of Cardiology, 36 (1992) 223-226 Q 1992 Elsevier Science Publishers B.V. All rights reserved
CARD10
223 0167-5273/92/$05.00
01486
Pacing termination of spontaneous ventricular tachycardia in the coronary care unit Keith G. Oldroyd,
Andrew
C. Rankin,
Alan P. Rae and Stuart M. Cobbe
Department of Medical Cardiology, UniL~ersi~of Glasgow: UK (Received
19 August
1991; revision
accepted
26 February
Oldroyd KG, Rankin AC, Rae AP, Cobbe SM. Pacing termination dia in the coronary care unit. Int J Cardiol 1992;36:223-226.
1992)
of spontaneous
ventricular tachycar-
We reviewed our experience with the use of pacing techniques in the acute treatment of spontaneous ventricular tachycardia occurring outside the context of acute myocardial ischaemia. Over a consecutive 18 month period 23 patients (20 male, aged 38-76 yr) admitted to our coronary care unit experienced a total of 75 episodes of haemodynamically tolerated sustained ventricular tachycardia. Pace termination was attempted in 18 patients in a total of 58 episodes of ventricular tachycardia using a standard temporary external pacemaker. Pacing was successful in 32/58 (55%) attempts vs 13/49 (27%) with intravenous antiarrhythmic drug therapy p = 0.003. The superior success rate of pacing was apparent whether or not patients were receiving chronic antiarrhythmic drug therapy. Pace termination should be considered in the treatment of haemodynamically tolerated spontaneous ventricular tachycardias. Key words: Ventricular
tachycardia;
Myocardial infarction; Antiarrhythmia
Introduction Pacing techniques can reliably terminate ventricular tachycardia induced during electrophysiological testing in around 60% of cases [1,2]. However, in the management of spontaneous ventricular tachycardia, most major textbooks recommend the intravenous administration of an antiarrhythmic drug as the first-line treatment [3,4]. This paper compares the efficacy of pacing techniques employed in the coronary care unit for the termi-
Correspondence to: Dr. K.G. Oldroyd, Dept. of Medical Cardiology, Royal Infirmary, 10 Alexandra Parade, Glasgow G31 2ER, UK. Tel. 041 552 3535. Fax 041 552 4783.
pacing
nation of spontaneous ventricular tachycardia with that of intravenous antiarrhythmic drugs. Patients and Methods We reviewed the case records of all patients admitted to the coronary care unit of the Glasgow Royal Infirmary over a consecutive 18 month period. Patients who had experienced one or more episodes of spontaneous haemodynamically tolerated sustained ventricular tachycardia occurring in the absence of evidence of acute myocardial ischaemia were identified. Pace termination was performed using a standard temporary external pulse generator (APC Type E4162) with a X .3 rate multiplier. A single 6F or 7F bipolar tempo-
224
rat-y pacing lead was passed transvenously to the right ventricular apex. Underdrive pacing was performed at fixed rates of between 80-100 beats per minute for periods of up to 2 min at twice diastolic threshold. Overdrive pacing was performed in demand mode in short bursts of up to 20 s duration starting at approximately 20 beats/min above the tachycardia rate and increasing the pacing rate until success was achieved or the patient became haemodynamically intolerant of the procedure. Either or both pacing modes or antiarrhythmic drugs were used in any order depending on the physician’s anticipation of success and the results of previous therapeutic interventions. If termination was not achieved the pulse amplitude was increased and the pace termination sequence repeated. Separate episodes of arrhythmia were defined by a preceding period of stable sinus rhythm of at least 10 min duration. Sequential administration of different antiarrhythmic drugs for the same episode of tachycardia were each counted separately. Repeat attempts to pace terminate the tachycardia after additional intravenous drug therapy were also counted separately. For the purposes of this review, acceleration of the tachycardia by pacing was defined as an increase in rate necessitating the use of emergency direct current cardioversion. The success rates of different therapies were compared using chi-square tests. Results During the 18 month period reviewed, 23 patients (20 male, aged 38-76 yr> experienced a total of 75 episodes of haemodynamically tolerated sustained ventricular tachycardia. Pace termination was attempted in 18 patients in a total of 58 episodes of ventricular tachycardia. The underlying diagnoses were: coronary heart disease (20), dilated cardiomyopathy (11, right ventricular dysplasia (1) and complex congenital heart disease (1). The 5 patients in whom pace termination was never attempted experienced a total of 6 episodes of sustained ventricular tachycardia. In these 5 patients, intravenous lignocaine therapy was successful in 2/6 attempts, one episode terminated spontaneously and the other 3 episodes
Fig. 1. Flow chart describing the therapy of 75 episodes of spontaneous sustained haemodynamically tolerated ventricular tachycardia. Pacing and drugs were both employed in 32 episodes. *: p = 0.003 vs drug therapy.
were terminated by direct current cardioversion. In the other 18 patients, the mean number of antiarrhythmic drugs administered, either acutely or chronically, prior to the first attempt at pace termination was 2.5 per patient (range O-6). A total of 30 pacing leads were inserted (range l-5 per patient) with the mean duration of insertion being 4 days (range l-17). The average number of episodes in which pace termination was attempted was 3.8 per patient (range l-12). No complications related to pacing lead insertion were observed. Considering all 75 episodes of sustained ventricular tachycardia, pacing terminated the arrhythmia more often than intravenous antiarrhythmic drug therapy, p = 0.003 (Fig. 1). Underdrive and overdrive pacing were equally effective. The most commonly used drug therapy was lignocaine which terminated the arrhythmia on 8/30 (27%) attempts. Fifteen patients experienced 18 episodes of ventricular tachycardia whilst on no antiarrhythmic therapy. In all of these episodes drug therapy was chosen as the initial treatment and produced sinus rhythm on 5/26 (19%) attempts vs 7/10 (70%) with pacing, p = 0.004. All of the other 57 episodes occurred whilst the patients were on chronic antiarrhythmic therapy. In these the initial treatment chosen was pacing (461, drugs (8) and direct current cardioversion (3). Drug therapy produced sinus rhythm on 6/26 (23%) attempts vs 26/48 (54%) with pacing, p = 0.01.
735
Tachycardia acceleration during attempted pace termination with a subsequent need for emergency direct current cardioversion occurred on 6 occasions. In 5 of these, acceleration occurred during overdrive pacing. In one, acceleration occurred during manipulation of the pacing electrode. The mean (SD) rate of the ventricular tachycardias which accelerated during attempted pace termination was 182 (29) beats per minute. One way analysis of variance revealed no statistically significant differences between this heart rate and the rates of the tachycardias which did and did not terminate with pacing: underdrive 165 (251 vs 168 (33) beats/min and overdrive 174 (29) vs 153 (27) beats/min, F = 1.61, p = 0.18. In uncorrected unpaired t tests, the differences between the rates of those tachycardias which failed to terminate with overdrive pacing and both those which did (p = 0.04) and those which accelerated ( p = 0.05) were of borderline significance. Discussion This article demonstrates that relatively simple and inexpensive pacing equipment can be used in the coronary care unit to terminate spontaneous ventricular tachycardia with a similar success rate to that achieved with induced ventricular tachycardia in the electrophysiological laboratory [ 1,2]. In a recent study of the relative safety and efficacy of various intravenous drugs used for the attempted termination of induced sustained ventricular tachycardia, success was achieved in only 35/105 (33%) drug trials. Lignocaine terminated the arrhythmia in 7/23 (30%) attempts [5]. These success rates compare with our own experience of antiarrhythmic drugs in spontaneous ventricular tachycardia and are considerably lower than those of pacing techniques. The use of pacing as the primary treatment option may avoid several of the problems associated with antiarrhythmic drug therapy, such as depression of ventricular function, proarrhythmia and interference with subsequent induction at electrophysiological testing. Concomitant antiarrhythmic drugs may also complicate the measurement of defibrillation thresholds in patients receiving implantable cardioverter/defibrillator devices. Other advantages
include a reduction in the need for repeated direct current cardioversions, bradycardia protection and the option of continuous ventricular pacing to suppress ectopic activity. A temporary pacing electrode also allows the ventricular origin of the tachycardia to be confirmed by simultaneous recording of the atria1 electrogram and the surface electrocardiogram. Problems associated with pacing include those associated with temporary pacing electrode insertion and the risk of acceleration of the tachycardia. Acceleration requiring direct current cardioversion occurred in 6 (10%) episodes, all in patients in whom antiarrhythmic drugs had failed and in whom direct current cardioversion was inevitable in the event of continued failure. The data on heart rate did not allow the application of a stricter definition of acceleration e.g. an increase of 10% or more in rate, but the definition we used is certainly clinically relevant. There did not seem to be an increased incidence of acceleration during underdrive pacing, despite the theoretical risk of introducing an extrastimulus during the vulnerable period of the ventricle. Clearly, this risk would be substantially reduced by the use of a programmable electrophysiological stimulator, but the purpose of this study was to demonstrate that it is possible to perform safely both underdrivc and overdrive pace termination of ventricular tachycardia in the coronary care unit without such equipment. Our rate data did suggest that as would be predicted the ventricular tachycardias which accelerated during attempted overdrive pace termination tended to be faster than those in which the technique failed. However, contrary to experience with induced ventricular tachycardia in the electrophysiology laboratory, the rates of the tachycardias in which overdrive pacing succeeded appeared also to be higher than those in which it failed. The reasons for this are not clear, but might relate to differences in neuroendocrine and autonomic activation between patients with induced and spontaneous ventricular tachycardia. In any case, it would be prudent to confirm this observation in a larger group of patients before seeking further explanations. Indications for the use of pacing as the primary treatment of haemodynamically tolerated
226
ventricular tachycardia should include a past history of drug resistant ventricular tachycardia or documented successful pace termination and/or anticipation of recurrent episodes of arrhythmia. In our patients drug therapy was preferentially used in patients who had not received prior antiarrhythmic drug therapy. By contrast pacing was used more often as the first line treatment in patients who had received prior antiarrhythmic drug therapy. This reflects concern over the potentially adverse effects of administering multiple antiarrhythmic agents. In either situation, notwithstanding the possible impact of any interaction between pacing and drug therapy, our data suggest that pacing may be the treatment of choice for the acute termination of haemodynamically tolerated spontaneous ventricular tachycardias.
References 1 Fisher JD, Mehra R, Furman S. Termination of ventricular tachycardia with bursts of ventricular pacing. Am J Cardiol 1978;41:94-102. 2 Brugada P, Wellens HJJ. Programmed electrical stimulation of the human heart. In: Josephson ME, Wellens HJJ. eds. Tachycardias: mechanism, diagnosis, treatment. Philadelphia: Lea and Febiger, 1984;61-89. 3 Bennett DH. Cardiac arrhythmias. In: Weatherall DJ, Ledingham JGG, Warrell DA, eds. Oxford textbook of medicine. ch 3. Oxford: Oxford University Press. 1983:7892. 4 Zipes DP. Specific arrhythmias: diagnosis and treatment. In: Braunwald E, ed. Heart disease. 3rd ed. Philadelphia: W.B. Saunders Company, 1988;658-716. 5 Griffith MJ, Linker NJ, Garratt CJ, Ward DE, Camm AJ. Relative efficacy and safety of intravenous drugs for termination of sustained ventricular tachycardia. Lancet 1990; 336(ii3:670-673.
CARD10
223 0167-5273/92/$05.00
01486
Pacing termination of spontaneous ventricular tachycardia in the coronary care unit Keith G. Oldroyd,
Andrew
C. Rankin,
Alan P. Rae and Stuart M. Cobbe
Department of Medical Cardiology, UniL~ersi~of Glasgow: UK (Received
19 August
1991; revision
accepted
26 February
Oldroyd KG, Rankin AC, Rae AP, Cobbe SM. Pacing termination dia in the coronary care unit. Int J Cardiol 1992;36:223-226.
1992)
of spontaneous
ventricular tachycar-
We reviewed our experience with the use of pacing techniques in the acute treatment of spontaneous ventricular tachycardia occurring outside the context of acute myocardial ischaemia. Over a consecutive 18 month period 23 patients (20 male, aged 38-76 yr) admitted to our coronary care unit experienced a total of 75 episodes of haemodynamically tolerated sustained ventricular tachycardia. Pace termination was attempted in 18 patients in a total of 58 episodes of ventricular tachycardia using a standard temporary external pacemaker. Pacing was successful in 32/58 (55%) attempts vs 13/49 (27%) with intravenous antiarrhythmic drug therapy p = 0.003. The superior success rate of pacing was apparent whether or not patients were receiving chronic antiarrhythmic drug therapy. Pace termination should be considered in the treatment of haemodynamically tolerated spontaneous ventricular tachycardias. Key words: Ventricular
tachycardia;
Myocardial infarction; Antiarrhythmia
Introduction Pacing techniques can reliably terminate ventricular tachycardia induced during electrophysiological testing in around 60% of cases [1,2]. However, in the management of spontaneous ventricular tachycardia, most major textbooks recommend the intravenous administration of an antiarrhythmic drug as the first-line treatment [3,4]. This paper compares the efficacy of pacing techniques employed in the coronary care unit for the termi-
Correspondence to: Dr. K.G. Oldroyd, Dept. of Medical Cardiology, Royal Infirmary, 10 Alexandra Parade, Glasgow G31 2ER, UK. Tel. 041 552 3535. Fax 041 552 4783.
pacing
nation of spontaneous ventricular tachycardia with that of intravenous antiarrhythmic drugs. Patients and Methods We reviewed the case records of all patients admitted to the coronary care unit of the Glasgow Royal Infirmary over a consecutive 18 month period. Patients who had experienced one or more episodes of spontaneous haemodynamically tolerated sustained ventricular tachycardia occurring in the absence of evidence of acute myocardial ischaemia were identified. Pace termination was performed using a standard temporary external pulse generator (APC Type E4162) with a X .3 rate multiplier. A single 6F or 7F bipolar tempo-
224
rat-y pacing lead was passed transvenously to the right ventricular apex. Underdrive pacing was performed at fixed rates of between 80-100 beats per minute for periods of up to 2 min at twice diastolic threshold. Overdrive pacing was performed in demand mode in short bursts of up to 20 s duration starting at approximately 20 beats/min above the tachycardia rate and increasing the pacing rate until success was achieved or the patient became haemodynamically intolerant of the procedure. Either or both pacing modes or antiarrhythmic drugs were used in any order depending on the physician’s anticipation of success and the results of previous therapeutic interventions. If termination was not achieved the pulse amplitude was increased and the pace termination sequence repeated. Separate episodes of arrhythmia were defined by a preceding period of stable sinus rhythm of at least 10 min duration. Sequential administration of different antiarrhythmic drugs for the same episode of tachycardia were each counted separately. Repeat attempts to pace terminate the tachycardia after additional intravenous drug therapy were also counted separately. For the purposes of this review, acceleration of the tachycardia by pacing was defined as an increase in rate necessitating the use of emergency direct current cardioversion. The success rates of different therapies were compared using chi-square tests. Results During the 18 month period reviewed, 23 patients (20 male, aged 38-76 yr> experienced a total of 75 episodes of haemodynamically tolerated sustained ventricular tachycardia. Pace termination was attempted in 18 patients in a total of 58 episodes of ventricular tachycardia. The underlying diagnoses were: coronary heart disease (20), dilated cardiomyopathy (11, right ventricular dysplasia (1) and complex congenital heart disease (1). The 5 patients in whom pace termination was never attempted experienced a total of 6 episodes of sustained ventricular tachycardia. In these 5 patients, intravenous lignocaine therapy was successful in 2/6 attempts, one episode terminated spontaneously and the other 3 episodes
Fig. 1. Flow chart describing the therapy of 75 episodes of spontaneous sustained haemodynamically tolerated ventricular tachycardia. Pacing and drugs were both employed in 32 episodes. *: p = 0.003 vs drug therapy.
were terminated by direct current cardioversion. In the other 18 patients, the mean number of antiarrhythmic drugs administered, either acutely or chronically, prior to the first attempt at pace termination was 2.5 per patient (range O-6). A total of 30 pacing leads were inserted (range l-5 per patient) with the mean duration of insertion being 4 days (range l-17). The average number of episodes in which pace termination was attempted was 3.8 per patient (range l-12). No complications related to pacing lead insertion were observed. Considering all 75 episodes of sustained ventricular tachycardia, pacing terminated the arrhythmia more often than intravenous antiarrhythmic drug therapy, p = 0.003 (Fig. 1). Underdrive and overdrive pacing were equally effective. The most commonly used drug therapy was lignocaine which terminated the arrhythmia on 8/30 (27%) attempts. Fifteen patients experienced 18 episodes of ventricular tachycardia whilst on no antiarrhythmic therapy. In all of these episodes drug therapy was chosen as the initial treatment and produced sinus rhythm on 5/26 (19%) attempts vs 7/10 (70%) with pacing, p = 0.004. All of the other 57 episodes occurred whilst the patients were on chronic antiarrhythmic therapy. In these the initial treatment chosen was pacing (461, drugs (8) and direct current cardioversion (3). Drug therapy produced sinus rhythm on 6/26 (23%) attempts vs 26/48 (54%) with pacing, p = 0.01.
735
Tachycardia acceleration during attempted pace termination with a subsequent need for emergency direct current cardioversion occurred on 6 occasions. In 5 of these, acceleration occurred during overdrive pacing. In one, acceleration occurred during manipulation of the pacing electrode. The mean (SD) rate of the ventricular tachycardias which accelerated during attempted pace termination was 182 (29) beats per minute. One way analysis of variance revealed no statistically significant differences between this heart rate and the rates of the tachycardias which did and did not terminate with pacing: underdrive 165 (251 vs 168 (33) beats/min and overdrive 174 (29) vs 153 (27) beats/min, F = 1.61, p = 0.18. In uncorrected unpaired t tests, the differences between the rates of those tachycardias which failed to terminate with overdrive pacing and both those which did (p = 0.04) and those which accelerated ( p = 0.05) were of borderline significance. Discussion This article demonstrates that relatively simple and inexpensive pacing equipment can be used in the coronary care unit to terminate spontaneous ventricular tachycardia with a similar success rate to that achieved with induced ventricular tachycardia in the electrophysiological laboratory [ 1,2]. In a recent study of the relative safety and efficacy of various intravenous drugs used for the attempted termination of induced sustained ventricular tachycardia, success was achieved in only 35/105 (33%) drug trials. Lignocaine terminated the arrhythmia in 7/23 (30%) attempts [5]. These success rates compare with our own experience of antiarrhythmic drugs in spontaneous ventricular tachycardia and are considerably lower than those of pacing techniques. The use of pacing as the primary treatment option may avoid several of the problems associated with antiarrhythmic drug therapy, such as depression of ventricular function, proarrhythmia and interference with subsequent induction at electrophysiological testing. Concomitant antiarrhythmic drugs may also complicate the measurement of defibrillation thresholds in patients receiving implantable cardioverter/defibrillator devices. Other advantages
include a reduction in the need for repeated direct current cardioversions, bradycardia protection and the option of continuous ventricular pacing to suppress ectopic activity. A temporary pacing electrode also allows the ventricular origin of the tachycardia to be confirmed by simultaneous recording of the atria1 electrogram and the surface electrocardiogram. Problems associated with pacing include those associated with temporary pacing electrode insertion and the risk of acceleration of the tachycardia. Acceleration requiring direct current cardioversion occurred in 6 (10%) episodes, all in patients in whom antiarrhythmic drugs had failed and in whom direct current cardioversion was inevitable in the event of continued failure. The data on heart rate did not allow the application of a stricter definition of acceleration e.g. an increase of 10% or more in rate, but the definition we used is certainly clinically relevant. There did not seem to be an increased incidence of acceleration during underdrive pacing, despite the theoretical risk of introducing an extrastimulus during the vulnerable period of the ventricle. Clearly, this risk would be substantially reduced by the use of a programmable electrophysiological stimulator, but the purpose of this study was to demonstrate that it is possible to perform safely both underdrivc and overdrive pace termination of ventricular tachycardia in the coronary care unit without such equipment. Our rate data did suggest that as would be predicted the ventricular tachycardias which accelerated during attempted overdrive pace termination tended to be faster than those in which the technique failed. However, contrary to experience with induced ventricular tachycardia in the electrophysiology laboratory, the rates of the tachycardias in which overdrive pacing succeeded appeared also to be higher than those in which it failed. The reasons for this are not clear, but might relate to differences in neuroendocrine and autonomic activation between patients with induced and spontaneous ventricular tachycardia. In any case, it would be prudent to confirm this observation in a larger group of patients before seeking further explanations. Indications for the use of pacing as the primary treatment of haemodynamically tolerated
226
ventricular tachycardia should include a past history of drug resistant ventricular tachycardia or documented successful pace termination and/or anticipation of recurrent episodes of arrhythmia. In our patients drug therapy was preferentially used in patients who had not received prior antiarrhythmic drug therapy. By contrast pacing was used more often as the first line treatment in patients who had received prior antiarrhythmic drug therapy. This reflects concern over the potentially adverse effects of administering multiple antiarrhythmic agents. In either situation, notwithstanding the possible impact of any interaction between pacing and drug therapy, our data suggest that pacing may be the treatment of choice for the acute termination of haemodynamically tolerated spontaneous ventricular tachycardias.
References 1 Fisher JD, Mehra R, Furman S. Termination of ventricular tachycardia with bursts of ventricular pacing. Am J Cardiol 1978;41:94-102. 2 Brugada P, Wellens HJJ. Programmed electrical stimulation of the human heart. In: Josephson ME, Wellens HJJ. eds. Tachycardias: mechanism, diagnosis, treatment. Philadelphia: Lea and Febiger, 1984;61-89. 3 Bennett DH. Cardiac arrhythmias. In: Weatherall DJ, Ledingham JGG, Warrell DA, eds. Oxford textbook of medicine. ch 3. Oxford: Oxford University Press. 1983:7892. 4 Zipes DP. Specific arrhythmias: diagnosis and treatment. In: Braunwald E, ed. Heart disease. 3rd ed. Philadelphia: W.B. Saunders Company, 1988;658-716. 5 Griffith MJ, Linker NJ, Garratt CJ, Ward DE, Camm AJ. Relative efficacy and safety of intravenous drugs for termination of sustained ventricular tachycardia. Lancet 1990; 336(ii3:670-673.