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Low energy counterchock using an intravascular catheter in an acute cardiac care setting
Low Energy Countershock Using an Intravascular Catheter In an Acute Cardiac Care Setting RAYMOND YEE, MD, DOUGLAS P . ZIPES, MD, SAJAD GULAMHUSEIN, MD, MICHAEL J . KALLOK, PhD, and GEORGE J . KLEIN, MD
We examined the feasibility, effectiveness, and safety of using an intravascular catheter positioned in the right ventricular apex for countershock in a coronary care unit setting in 8 patients who had recurrent ventricular tachyarrhythmia . Countershock using 2 .5 to 40 J stored energy (damped sinusoidal wave form) was attempted 115 times to terminate 100 episodes of ventricular tachyarrhythmia (ventricular tachycardia, 91 ; ventricular flutter, 3 ; ventricular fibrillation, 6) . Eighty-six (87 % ) of 99 countershock attempts for ventricular tachycardia, 3 (60%) of 5 for ventricular flutter, and 4 (36%) of 11 for ventricular fibrillation were successful using this technique . The catheters remained
in stable position for 1 to 16 days without dislodgment. A majority of the countershocks were delivered by the regular nursing staff in the coronary unit . We conclude that low energy countershock through an intravascular catheter system is feasible, safe, and effective in a coronary care unit setting . Such a system should be beneficial in the acute management of patients who have recurrent ventricular tachycardia or fibrillation . The catheter lead may also prove useful in managing ventricular tachyarrhythmias that occur during electrophysiologic studies .
Patients with unstable cardiac disease may experience frequently recurring ventricular arrhythmias requiring repeated external countershock while appropriate medical management is being instituted . Repetitive countershocks can be psychologically and physically traumatic for these patients and may be associated with a risk of further myocardial necrosis .' The pressure on the medical staff to control arrhythmias quickly under these circumstances may result in the overzealous use of antiarrhythmic agents with increased risk of drug toxicity . We studied the feasibility, effectiveness, and safety of using an intravascular catheter lead system to help control arrhythmias in 8 patients referred for management of frequently recurring, sustained ventricular
tachyarrhythmia . In particular, we assessed the usefulness of this catheter system for overdrive termination of ventricular tachycardia, low energy cardioversion, and defibrillation and temporary pacing in the event of bradycardia .
From the Department of Medicine, Division of Cardiology, University Hospital, London, Ontario . This study was supported in part by funds from the Ontario Heart Foundation, Toronto, Ontario, Canada . Manuscript received February 22, 1982 ; revised manuscript received April 19, 1982, accepted April 26, 1982 . Address for reprints : George J. Klein, MD, Cardiac Investigation Unit, University Hospital, PO Box 5339, Station A, London, Ontario, Canada N6A 5A5 .
1124
November 1982
Methods Patients: All patients were referred to the Coronary Care Unit at University Hospital for the management of recurrent ventricular tachycardia or fibrillation requiring 1 to 20 external countershocks before transfer (Table I) . Prior approval for the use of the countershock catheter in such patients was obtained from the Ethics Committee at The University of Western Ontario. Written, informed consent was obtained from each patient . All 8 patients were men, aged 35 to 63 years . Six patients had coronary heart disease (2 with acute myocardial infarction) and 2 patients had cardiomyopathy . Six of these 8 patients developed ventricular arrhythmia requiring countershock . Description of the catheter system : The countershock lead (Medtronic, DFX-2) is a tripolar 9 .5Fr, 100 cm polyether urethane catheter (Fig . 1) with a central lumen for guide wire manipulation . The catheter has 4 stainless steel electrode sleeves, each with a surface area of 125 mm 2. The most distal electrode sleeve (A) is located at the catheter tip, and a second
The American Journal of CARDIOLOGY Volume 50
CATHETER DEFIBRILLATION-YEE ET AL .
TABLE I
Patient Population Data
Case
Age (yr) & Sex
Weight (kg)
1
58M
75
2
57M
63
3 4 5
56M 40M 63M
82 61 70
6 7 8
55M 35M 63M
79 57 73
Diagnosis CAD, LV aneurysm AMI, LV aneurysm AMI Cardiomyopathy CAD, LV aneurysm CAD Cardiomyopathy CAD, LV aneurysm
Total
External CS Attempts
VTA Episodes Requiring Catheter Lead CS
CTR
Lead Duration (Days)
R Wave (mV)
VT
VFL
4
0 .46
5
5
2
1
9
0 .52
16
20
78
...
4
82
20 3 6
0 .57 • 0 .51 • 0 .60
1 9 11
5 .3 2 15
1 1 7
2 .. . .. .
2
5 1 7
1 2 1
0 .51' 0 .54 0 .48
1 1 1
5 1 .7 3.6
2
. .. .. . . . .
.. .
.. .
91
3
VF
Total 3
0 0 2 6
100
" Portable chest roentgenogram . AMI = acute myocardial infarction ; CAD = coronary artery disease ; CTR = cardiothoracic ratio ; External CS = number of transthoracic countershock attempts before insertion of lead ; R wave = R-wave amplitude measured from catheter distal electrode ; VF = ventricular fibrillation ; VFL = ventricular flutter ; VT = ventricular tachycardia ; VTA = ventricular tachyarrhythmia .
electrode sleeve (B) is located 5 mm proximally . The other 2 sleeves, separated by a distance of 5 mm (C and D), are located 100 mm from sleeve B and constitute a single electrode . Each electrode is connected by a separate conductor coil wire to 1 of 3 connector pins at the proximal end of the catheter. In situ, the distal electrodes (A and B) are positioned in the right ventricular apex and the proximal electrode sleeves (C and D) are located approximately at the junction of the superior vena cava and the right atrium (Fig . 2) . The distal poles A and B can be used as a bipolar pacing pair . For defibrillation and cardioversion, electrodes A and B become common (the cathode) and the proximal electrodes (C and D) become the anode . The catheter was inserted employing a standard percutaneous introducer into the left subclavian vein and advanced using fluoroscopy to the right ventricular apex . After insertion, the amplitude of the R wave recorded from the distal elec-
trodes (A and B) was measured daily as one index of lead dislodgment, using a Medtronic 5300 pacing system analyzer. Lead position was verified every 12 to 24 hours by a chest radiograph (Fig . 2) . The lead was then interfaced to a commercially available Hewlett-Packard 78619A defibrillation unit, which produces a damped sinusoidal discharge wave form, through a switch box and current attenuator constructed in the University Hospital Biomedical Engineering Department . A programmable stimulating device or temporary pacemaker was connected to the distal electrode pair by the switching box . Protocol : Coronary care unit nurses and house-staff were instructed in the proper operation of the unit before each change of shift . Upon recognition of sustained ventricular tachyarrhythmia, the staff was instructed to deliver shocks in incremental doses until successful reversion to sinus rhythm occurred. Energy levels 2 .5, 5 .0, 7 .5,10,15, 20, 30, and 40 J were
FIGURE 1 . Tripolar countershock catheter . A = distal right ventricular electrode sleeve ; B = proximal right ventricular electrode sleeve ; C and D = proximal superior vena cava/right atrial electrode sleeves ; I = distal right ventricular electrode connector pin ; II = proximal right ventricular connector pin ; III = superior vena cava/right atrial electrode connector pin (see text) .
November 1982 The American Journal of CARDIOLOGY Volume 50
1 125
CATHETER DEFIBRILLATION-YEE ET AL .
TABLE II Analysis
of
Countershock Attempts With
Intravascular Lead*
Energy Dose (J) Total Case Attempts VT
2
VT VF VT
5 1
VFL
2
VF
6
0/1
4
VT
1
1/1
5
VT
8
7/8
VFL
3
6
15-40
2/2
3
0/2
1/1
84
1/2
73/80
0/2
1/1
0/1
2/3
. .
0/1 2/2 1/5
.
8
VT
3
Totals
VT
99
VFL
5
VF _J_1 115
7.5-10
2
. . .
7
Chest roentgenogram illustrating proper placement of tripolar lead with the catheter tip in the right ventricular apex and proximal electrode at the junction of the right atrium and superior vena cava.
2 .5-5 .0
1
1/2
1/1
12/16 0/2
73/80 1/1
2/2 = 3/5
1/2
0/1
X$=
13/20(65%)
1 /3 = 86/99 (87%)
74/82(90%)
(60%)
4/11 (36%)
6/13(46%)
Numerators = number of successful countershock attempts at specified energy dose ; denominators = total number of countershock attempts delivered ; VF = ventricular fibrillation ; VFL = ventricular flutter ; VT = ventricular tachycardia .
FIGURE 2.
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Patient 5 . Burst ventricular pacing using countershock catheter . Ventricular tachycardia at cycle length 520 ms Is entrained by pacing stimuli (arrows) at a cycle length of 500 ms . Abrupt termination of pacing results in restoration of sinus rhythm .
FIGURE 3 .
Patient 2 . Cardioversion using intravascular catheter countershock at 5 J. A lead II monitor strip shows 11 beats of ventricular tachycardia . A synchronized 5 J discharge is delivered, restoring sinus rhythm .
FIGURE 4.
chosen and delivered in the synchronized (for ventricular tachycardia and flutter) or nonsynchronized mode (ventricular fibrillation) . A second conventional Hewlett-Packard 78619A defibrillator was available for back-up transthoracic shocks . The initial energy dose selected was 5 J for ventricular tachycardia and flutter, while defibrillation attempts for ventricular fibrillation started at 10 J . After 5 consecutive successful attempts, the coronary care unit staff was instructed to reduce the energy used to the next lower level . However, if any failures occurred, the dose was doubled and not reduced until 5 consecutive successful attempts were attained . While every attempt was made to adhere to this protocol, use of transthoracic countershock at any earlier time was left to the discretion of the staff at the bedside based upon the clinical status and hemodynamic stability of the patient during tachycardia. "Burst" pacing through the catheter was attempted in 1 patient (Patient 5) with recurring episodes of ventricular tachycardia using a stimulus cycle length of 500 ms and current output of 15 mA . Serial measurement of serum creatine kinase, lactic dehydrogenase, or glutamic oxaloacetic transaminase as an index
of possible myocardial injury secondary to catheter countershock was not conducted . We could not reliably attribute elevations in enzyme levels to this technique since patients had received transthoracic countershock before insertion of the catheter and some had had an acute myocardial infarction .
1 12 6
Results The catheter was inserted in 8 patients (Table I) . Lead insertion was carried out uneventfully in the coronary care unit (5 patients) or in the electrophysiology laboratory (3 patients) . Leads remained in position 1 to 16 days without a single lead displacement . Six of the 8 patients developed ventricular tachyarrhythmia requiring use of the countershock catheter. Ventricular tachycardia : Synchronized cardioversion was attempted 99 times for 91 episodes of ventricular tachycardia (Fig . 3, Table II) . Eighty-six (87%) of these attempts successfully terminated tachycardia using energy levels of 10 J or less . In 1 patient burst ventricular pacing was utilized to terminate ventricular tachycardia and was successful in 10 of 14 attempts (Fig .
November 1982 The American Journal of CARDIOLOGY Volume 50
CATHETER DEFIBRILLATION-YEE ET AL .
1 Isecl 25J
I Isecl
V FIGURE 5. Continuous intracardiac recordings of ventricular tachycardia at electrophysiologic study . V Top, the recording begins with ventricular tachycardia. The introduction of 2 premature ventricular stimuli (arrows) to terminate the tachyarrhythmia results in acceleration followed by a change in morphology of the tachycardia and hemodynamic deterioration . Catheter countershock attempt H B using 2 .5 J fails to terminate ventricular tachycardia. Bottom, a second attempt using 5 .0 J delivered through catheter lead also fails, but 7 .5 J energy dose terminates ventricular tachycardia and restores sinus rhythm .
4) . However, the use of programmed ventricular extrastimuli to terminate stable ventricular tachycardia in another patient led to acceleration of tachycardia with hemodynamic collapse (Fig . 5, top), necessitating the use of cardioversion by means of the catheter (Fig . 5, bottom) . Energy doses of 10 J or less failed to terminate 3 episodes of ventricular tachycardia (Patients 2, 3, and 5) and 2 other episodes did not terminate after 20 J (Patient 2) . Transthoracic cardioversion using 200 J converted all 5 episodes . Ventricular flutter and fibrillation: All 3 episodes of ventricular flutter occurring in 2 patients were converted with synchronized shocks of 7 .5 J in 1 and 15 J in the other after a total of 5 attempts (Table II) . There were 6 episodes of ventricular fibrillation requiring 11 attempts at catheter countershock . Four episodes were successfully terminated (Fig . 6), 1 at 5 J and 3 at 40 J .
In 1 of the 2 failures (Patient 2), conventional defibrillation at 400 J successfully restored sinus rhythm . The second failure involving Patient 3 occurred as a preterminal event . Several attempts at conventional countershock in this patient resulted in asystole . In spite of successful pacing using an indwelling catheter, no cardiac output could be obtained . Discomfort associated with catheter defibrillation : Discomfort was difficult to assess because most patients had a diminished level of consciousness at the time of countershock . However, shocks of 2 .5 J were associated with a visible chest thrusting . One patient described a 2 .5 J countershock as a "kick in the chest ." Clinical outcome : Satisfactory arrhythmia control was ultimately obtained in all 6 surviving patients . Two patients died in hospital with the catheter lead in situ . At the time of death, the lead was in satisfactory posi-
November 1982
The American Journal of CARDIOLOGY
Volume 50
1127
CATHETER DEFIBRILLATION-YEE ET AL .
FIGURE 6 . Patient 2. A continuous rhythm (lead II) strip shows sinus rhythm initially, with spontaneous development of ventricular fibrillation . Delivery of 5 J nonsynchronized shock using the catheter lead restores sinus rhythm .
i
tion in the right ventricular apex in both patients despite prolonged attempts at cardiopulmonary resuscitation . In 1 patient (Patient 3), a focal area of endocardial hemorrhage measuring less than 2 mm 2 was visible at the site of the proximal electrode (C and D) . No gross or microscopic injury could be identified at the right ventricular apex . This patient had received 9 countershocks (25 to 40 J) . The second patient had no identifiable injury as a result of 8 countershocks (2 .5 to 5 .0 J) .
Discussion Advantages of method : Patients with frequently recurring sustained ventricular tachyarrhythmia may require repeated cardioversion or defibrillation while effective antiarrhythmic management is being instituted . We have shown that the use of low energy countershock delivered through an intravascular catheter lead is feasible, effective, and safe in this setting . The countershock lead can be inserted with the relative ease of a temporary pacing lead and remains stable after initial placement . The system described offers several advantages over the conventional method of countershock . First, relatively low energy levels can be used with a potential for less myocardial necrosis after repeated countershocks.l Second, the catheter can be connected to a programmable stimulator for conversion of ventricular tachycardia by burst pacing or ventricular extrastimuli . Defibrillation can be carried out through the catheter in the event of acceleration of tachycardia . Third, the catheter can be used for pacing in the event of bradycardia or asystole . Finally, defibrillation can be carried out expediently with the patient in any position without the delay of placing paddles . Finally, low energy countershock is probably less traumatic to the still-
1 128
November 1982
The American Journal of CARDIOLOGY
conscious patient with deteriorating cardiac output than conventional countershock . It is certain that the energies used for countershock in this study were greater than the minimal required energies using the catheter system . 2 . 3 Using our countershock system, we could not be certain of accuracy using stored energy less than 2 .5 J . Furthermore, most countershocks were delivered by intensive care nursing personnel who could not be asked to titrate the minimal energy in patients with hemodynamic deterioration . Comparison with previous lead systems: In 1970, Mirowski et a1. 4 introduced the concept of an automatic internal defibrillator and conceived a lead system wherein a catheter placed at the right ventricular apex had 1 electrode in the right ventricle and a second separate electrode consisting of an apical subcutaneous plate . Subsequent designs incorporated both electrodes onto a single catheter, 5 s and studies with various electrode positions demonstrated that the greatest efficacy of defibrillation was obtained when the distal electrode was placed in the right ventricular apex .? The optimal position of the proximal electrode (whether in the high right atrium or superior vena cava) was less critical so long as sufficient electrode surface area was present . However, in a review of their experience with the catheter mounted bielectrode lead, Mirowski et al . 8 noted that lead dislodgment was a significant problem leading to failure to defibrillate . We did not encounter lead displacement with the catheter (Medtronic DFX-2) used in this study . Newer prototypes of this catheter using fixation systems should minimize the problem of dislodgment. Implications : Low energy countershock using an intravascular catheter is feasible in a clinical setting . Pacing, programmed stimulation, cardioversion, and
Volume 50
CATHETER DEFIBRILLATION-YEE ET AL .
defibrillation can be performed with the catheter, resulting in more expedient arrhythmia management . In addition to its usefulness in the acute care setting, this technique could be adapted for use during electrophysiologic studies where ventricular tachyarrhythmia is anticipated . Finally, the potential exists for a completely "automated" bedside unit connected to the defibrillating catheter capable of detecting and treating both bradyarrhythmia and ventricular tachyarrhythmia . Acknowledgment We are grateful to the staff of the University Hospital Coronary Care Unit for their assistance, University Hospital Instructional Resources for illustrations, and Suzanne Stewart for manuscript preparation .
References 1 . Dahl C, Ewy GA, Warner ED, Thomas ED . Myocardial necrosis from direct current countershock : effect of paddle electrode size and time interval between discharges . Circulation 1974 ;50 :956-961 . 2. Zipes DP, Jackman WM, Heger JJ, et al . Transvenous cardioversion of ventricular tachycardia and termination of ventricular fibrillation in man (abstr) . Am J Cardiol 1982 ;49 :1022 . . 3 Jackman WM, Zipes DP. Low energy synchronous cardioversion of ventricular tachycardia using a catheter electrode in a canine model of subacute myocardial infarction . Circulation 1982 ;66 :187-195 . 4. Mirowski M, Mower M, Slaewen WS, Tabatznlk B, Mendeloff Al . Standby automatic defibrillator . Arch Intern Mad 1970 ;126 :158-161 . 5 . Schuder JC, Sloeckle H, West JA, Keskar PY, Gold JH . Ventricular defibrillation in the dog with a bielectrode intravascular catheter . Arch Intern Med 1973 ; 132 :286-290 . 6 . Denniston RH, Mower M, Mirowski M . Automatic standby defibrillator (abstr) . J Assoc Adv Med Instrum 1971 ;5 :110 . 7 . Schuder JC, Stoeckle H, West JA, Keskar PY . Relationship between electrode geometry and effectiveness of ventricular defibrillation in the dog having one electrode in the right ventricle and other electrode in the superior vena cava or external jugular vein or both . Cardiovasc Res 1973 ;7 :629637 . 8 . Mirowski M . Implanted Defibrillators . Proceedings of Purdue Cardiac Defibrillation Conference, 1975 .
November 1982 The American Journal of CARDIOLOGY Volume 50
1129
We examined the feasibility, effectiveness, and safety of using an intravascular catheter positioned in the right ventricular apex for countershock in a coronary care unit setting in 8 patients who had recurrent ventricular tachyarrhythmia . Countershock using 2 .5 to 40 J stored energy (damped sinusoidal wave form) was attempted 115 times to terminate 100 episodes of ventricular tachyarrhythmia (ventricular tachycardia, 91 ; ventricular flutter, 3 ; ventricular fibrillation, 6) . Eighty-six (87 % ) of 99 countershock attempts for ventricular tachycardia, 3 (60%) of 5 for ventricular flutter, and 4 (36%) of 11 for ventricular fibrillation were successful using this technique . The catheters remained
in stable position for 1 to 16 days without dislodgment. A majority of the countershocks were delivered by the regular nursing staff in the coronary unit . We conclude that low energy countershock through an intravascular catheter system is feasible, safe, and effective in a coronary care unit setting . Such a system should be beneficial in the acute management of patients who have recurrent ventricular tachycardia or fibrillation . The catheter lead may also prove useful in managing ventricular tachyarrhythmias that occur during electrophysiologic studies .
Patients with unstable cardiac disease may experience frequently recurring ventricular arrhythmias requiring repeated external countershock while appropriate medical management is being instituted . Repetitive countershocks can be psychologically and physically traumatic for these patients and may be associated with a risk of further myocardial necrosis .' The pressure on the medical staff to control arrhythmias quickly under these circumstances may result in the overzealous use of antiarrhythmic agents with increased risk of drug toxicity . We studied the feasibility, effectiveness, and safety of using an intravascular catheter lead system to help control arrhythmias in 8 patients referred for management of frequently recurring, sustained ventricular
tachyarrhythmia . In particular, we assessed the usefulness of this catheter system for overdrive termination of ventricular tachycardia, low energy cardioversion, and defibrillation and temporary pacing in the event of bradycardia .
From the Department of Medicine, Division of Cardiology, University Hospital, London, Ontario . This study was supported in part by funds from the Ontario Heart Foundation, Toronto, Ontario, Canada . Manuscript received February 22, 1982 ; revised manuscript received April 19, 1982, accepted April 26, 1982 . Address for reprints : George J. Klein, MD, Cardiac Investigation Unit, University Hospital, PO Box 5339, Station A, London, Ontario, Canada N6A 5A5 .
1124
November 1982
Methods Patients: All patients were referred to the Coronary Care Unit at University Hospital for the management of recurrent ventricular tachycardia or fibrillation requiring 1 to 20 external countershocks before transfer (Table I) . Prior approval for the use of the countershock catheter in such patients was obtained from the Ethics Committee at The University of Western Ontario. Written, informed consent was obtained from each patient . All 8 patients were men, aged 35 to 63 years . Six patients had coronary heart disease (2 with acute myocardial infarction) and 2 patients had cardiomyopathy . Six of these 8 patients developed ventricular arrhythmia requiring countershock . Description of the catheter system : The countershock lead (Medtronic, DFX-2) is a tripolar 9 .5Fr, 100 cm polyether urethane catheter (Fig . 1) with a central lumen for guide wire manipulation . The catheter has 4 stainless steel electrode sleeves, each with a surface area of 125 mm 2. The most distal electrode sleeve (A) is located at the catheter tip, and a second
The American Journal of CARDIOLOGY Volume 50
CATHETER DEFIBRILLATION-YEE ET AL .
TABLE I
Patient Population Data
Case
Age (yr) & Sex
Weight (kg)
1
58M
75
2
57M
63
3 4 5
56M 40M 63M
82 61 70
6 7 8
55M 35M 63M
79 57 73
Diagnosis CAD, LV aneurysm AMI, LV aneurysm AMI Cardiomyopathy CAD, LV aneurysm CAD Cardiomyopathy CAD, LV aneurysm
Total
External CS Attempts
VTA Episodes Requiring Catheter Lead CS
CTR
Lead Duration (Days)
R Wave (mV)
VT
VFL
4
0 .46
5
5
2
1
9
0 .52
16
20
78
...
4
82
20 3 6
0 .57 • 0 .51 • 0 .60
1 9 11
5 .3 2 15
1 1 7
2 .. . .. .
2
5 1 7
1 2 1
0 .51' 0 .54 0 .48
1 1 1
5 1 .7 3.6
2
. .. .. . . . .
.. .
.. .
91
3
VF
Total 3
0 0 2 6
100
" Portable chest roentgenogram . AMI = acute myocardial infarction ; CAD = coronary artery disease ; CTR = cardiothoracic ratio ; External CS = number of transthoracic countershock attempts before insertion of lead ; R wave = R-wave amplitude measured from catheter distal electrode ; VF = ventricular fibrillation ; VFL = ventricular flutter ; VT = ventricular tachycardia ; VTA = ventricular tachyarrhythmia .
electrode sleeve (B) is located 5 mm proximally . The other 2 sleeves, separated by a distance of 5 mm (C and D), are located 100 mm from sleeve B and constitute a single electrode . Each electrode is connected by a separate conductor coil wire to 1 of 3 connector pins at the proximal end of the catheter. In situ, the distal electrodes (A and B) are positioned in the right ventricular apex and the proximal electrode sleeves (C and D) are located approximately at the junction of the superior vena cava and the right atrium (Fig . 2) . The distal poles A and B can be used as a bipolar pacing pair . For defibrillation and cardioversion, electrodes A and B become common (the cathode) and the proximal electrodes (C and D) become the anode . The catheter was inserted employing a standard percutaneous introducer into the left subclavian vein and advanced using fluoroscopy to the right ventricular apex . After insertion, the amplitude of the R wave recorded from the distal elec-
trodes (A and B) was measured daily as one index of lead dislodgment, using a Medtronic 5300 pacing system analyzer. Lead position was verified every 12 to 24 hours by a chest radiograph (Fig . 2) . The lead was then interfaced to a commercially available Hewlett-Packard 78619A defibrillation unit, which produces a damped sinusoidal discharge wave form, through a switch box and current attenuator constructed in the University Hospital Biomedical Engineering Department . A programmable stimulating device or temporary pacemaker was connected to the distal electrode pair by the switching box . Protocol : Coronary care unit nurses and house-staff were instructed in the proper operation of the unit before each change of shift . Upon recognition of sustained ventricular tachyarrhythmia, the staff was instructed to deliver shocks in incremental doses until successful reversion to sinus rhythm occurred. Energy levels 2 .5, 5 .0, 7 .5,10,15, 20, 30, and 40 J were
FIGURE 1 . Tripolar countershock catheter . A = distal right ventricular electrode sleeve ; B = proximal right ventricular electrode sleeve ; C and D = proximal superior vena cava/right atrial electrode sleeves ; I = distal right ventricular electrode connector pin ; II = proximal right ventricular connector pin ; III = superior vena cava/right atrial electrode connector pin (see text) .
November 1982 The American Journal of CARDIOLOGY Volume 50
1 125
CATHETER DEFIBRILLATION-YEE ET AL .
TABLE II Analysis
of
Countershock Attempts With
Intravascular Lead*
Energy Dose (J) Total Case Attempts VT
2
VT VF VT
5 1
VFL
2
VF
6
0/1
4
VT
1
1/1
5
VT
8
7/8
VFL
3
6
15-40
2/2
3
0/2
1/1
84
1/2
73/80
0/2
1/1
0/1
2/3
. .
0/1 2/2 1/5
.
8
VT
3
Totals
VT
99
VFL
5
VF _J_1 115
7.5-10
2
. . .
7
Chest roentgenogram illustrating proper placement of tripolar lead with the catheter tip in the right ventricular apex and proximal electrode at the junction of the right atrium and superior vena cava.
2 .5-5 .0
1
1/2
1/1
12/16 0/2
73/80 1/1
2/2 = 3/5
1/2
0/1
X$=
13/20(65%)
1 /3 = 86/99 (87%)
74/82(90%)
(60%)
4/11 (36%)
6/13(46%)
Numerators = number of successful countershock attempts at specified energy dose ; denominators = total number of countershock attempts delivered ; VF = ventricular fibrillation ; VFL = ventricular flutter ; VT = ventricular tachycardia .
FIGURE 2.
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Patient 5 . Burst ventricular pacing using countershock catheter . Ventricular tachycardia at cycle length 520 ms Is entrained by pacing stimuli (arrows) at a cycle length of 500 ms . Abrupt termination of pacing results in restoration of sinus rhythm .
FIGURE 3 .
Patient 2 . Cardioversion using intravascular catheter countershock at 5 J. A lead II monitor strip shows 11 beats of ventricular tachycardia . A synchronized 5 J discharge is delivered, restoring sinus rhythm .
FIGURE 4.
chosen and delivered in the synchronized (for ventricular tachycardia and flutter) or nonsynchronized mode (ventricular fibrillation) . A second conventional Hewlett-Packard 78619A defibrillator was available for back-up transthoracic shocks . The initial energy dose selected was 5 J for ventricular tachycardia and flutter, while defibrillation attempts for ventricular fibrillation started at 10 J . After 5 consecutive successful attempts, the coronary care unit staff was instructed to reduce the energy used to the next lower level . However, if any failures occurred, the dose was doubled and not reduced until 5 consecutive successful attempts were attained . While every attempt was made to adhere to this protocol, use of transthoracic countershock at any earlier time was left to the discretion of the staff at the bedside based upon the clinical status and hemodynamic stability of the patient during tachycardia. "Burst" pacing through the catheter was attempted in 1 patient (Patient 5) with recurring episodes of ventricular tachycardia using a stimulus cycle length of 500 ms and current output of 15 mA . Serial measurement of serum creatine kinase, lactic dehydrogenase, or glutamic oxaloacetic transaminase as an index
of possible myocardial injury secondary to catheter countershock was not conducted . We could not reliably attribute elevations in enzyme levels to this technique since patients had received transthoracic countershock before insertion of the catheter and some had had an acute myocardial infarction .
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Results The catheter was inserted in 8 patients (Table I) . Lead insertion was carried out uneventfully in the coronary care unit (5 patients) or in the electrophysiology laboratory (3 patients) . Leads remained in position 1 to 16 days without a single lead displacement . Six of the 8 patients developed ventricular tachyarrhythmia requiring use of the countershock catheter. Ventricular tachycardia : Synchronized cardioversion was attempted 99 times for 91 episodes of ventricular tachycardia (Fig . 3, Table II) . Eighty-six (87%) of these attempts successfully terminated tachycardia using energy levels of 10 J or less . In 1 patient burst ventricular pacing was utilized to terminate ventricular tachycardia and was successful in 10 of 14 attempts (Fig .
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1 Isecl 25J
I Isecl
V FIGURE 5. Continuous intracardiac recordings of ventricular tachycardia at electrophysiologic study . V Top, the recording begins with ventricular tachycardia. The introduction of 2 premature ventricular stimuli (arrows) to terminate the tachyarrhythmia results in acceleration followed by a change in morphology of the tachycardia and hemodynamic deterioration . Catheter countershock attempt H B using 2 .5 J fails to terminate ventricular tachycardia. Bottom, a second attempt using 5 .0 J delivered through catheter lead also fails, but 7 .5 J energy dose terminates ventricular tachycardia and restores sinus rhythm .
4) . However, the use of programmed ventricular extrastimuli to terminate stable ventricular tachycardia in another patient led to acceleration of tachycardia with hemodynamic collapse (Fig . 5, top), necessitating the use of cardioversion by means of the catheter (Fig . 5, bottom) . Energy doses of 10 J or less failed to terminate 3 episodes of ventricular tachycardia (Patients 2, 3, and 5) and 2 other episodes did not terminate after 20 J (Patient 2) . Transthoracic cardioversion using 200 J converted all 5 episodes . Ventricular flutter and fibrillation: All 3 episodes of ventricular flutter occurring in 2 patients were converted with synchronized shocks of 7 .5 J in 1 and 15 J in the other after a total of 5 attempts (Table II) . There were 6 episodes of ventricular fibrillation requiring 11 attempts at catheter countershock . Four episodes were successfully terminated (Fig . 6), 1 at 5 J and 3 at 40 J .
In 1 of the 2 failures (Patient 2), conventional defibrillation at 400 J successfully restored sinus rhythm . The second failure involving Patient 3 occurred as a preterminal event . Several attempts at conventional countershock in this patient resulted in asystole . In spite of successful pacing using an indwelling catheter, no cardiac output could be obtained . Discomfort associated with catheter defibrillation : Discomfort was difficult to assess because most patients had a diminished level of consciousness at the time of countershock . However, shocks of 2 .5 J were associated with a visible chest thrusting . One patient described a 2 .5 J countershock as a "kick in the chest ." Clinical outcome : Satisfactory arrhythmia control was ultimately obtained in all 6 surviving patients . Two patients died in hospital with the catheter lead in situ . At the time of death, the lead was in satisfactory posi-
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FIGURE 6 . Patient 2. A continuous rhythm (lead II) strip shows sinus rhythm initially, with spontaneous development of ventricular fibrillation . Delivery of 5 J nonsynchronized shock using the catheter lead restores sinus rhythm .
i
tion in the right ventricular apex in both patients despite prolonged attempts at cardiopulmonary resuscitation . In 1 patient (Patient 3), a focal area of endocardial hemorrhage measuring less than 2 mm 2 was visible at the site of the proximal electrode (C and D) . No gross or microscopic injury could be identified at the right ventricular apex . This patient had received 9 countershocks (25 to 40 J) . The second patient had no identifiable injury as a result of 8 countershocks (2 .5 to 5 .0 J) .
Discussion Advantages of method : Patients with frequently recurring sustained ventricular tachyarrhythmia may require repeated cardioversion or defibrillation while effective antiarrhythmic management is being instituted . We have shown that the use of low energy countershock delivered through an intravascular catheter lead is feasible, effective, and safe in this setting . The countershock lead can be inserted with the relative ease of a temporary pacing lead and remains stable after initial placement . The system described offers several advantages over the conventional method of countershock . First, relatively low energy levels can be used with a potential for less myocardial necrosis after repeated countershocks.l Second, the catheter can be connected to a programmable stimulator for conversion of ventricular tachycardia by burst pacing or ventricular extrastimuli . Defibrillation can be carried out through the catheter in the event of acceleration of tachycardia . Third, the catheter can be used for pacing in the event of bradycardia or asystole . Finally, defibrillation can be carried out expediently with the patient in any position without the delay of placing paddles . Finally, low energy countershock is probably less traumatic to the still-
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conscious patient with deteriorating cardiac output than conventional countershock . It is certain that the energies used for countershock in this study were greater than the minimal required energies using the catheter system . 2 . 3 Using our countershock system, we could not be certain of accuracy using stored energy less than 2 .5 J . Furthermore, most countershocks were delivered by intensive care nursing personnel who could not be asked to titrate the minimal energy in patients with hemodynamic deterioration . Comparison with previous lead systems: In 1970, Mirowski et a1. 4 introduced the concept of an automatic internal defibrillator and conceived a lead system wherein a catheter placed at the right ventricular apex had 1 electrode in the right ventricle and a second separate electrode consisting of an apical subcutaneous plate . Subsequent designs incorporated both electrodes onto a single catheter, 5 s and studies with various electrode positions demonstrated that the greatest efficacy of defibrillation was obtained when the distal electrode was placed in the right ventricular apex .? The optimal position of the proximal electrode (whether in the high right atrium or superior vena cava) was less critical so long as sufficient electrode surface area was present . However, in a review of their experience with the catheter mounted bielectrode lead, Mirowski et al . 8 noted that lead dislodgment was a significant problem leading to failure to defibrillate . We did not encounter lead displacement with the catheter (Medtronic DFX-2) used in this study . Newer prototypes of this catheter using fixation systems should minimize the problem of dislodgment. Implications : Low energy countershock using an intravascular catheter is feasible in a clinical setting . Pacing, programmed stimulation, cardioversion, and
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defibrillation can be performed with the catheter, resulting in more expedient arrhythmia management . In addition to its usefulness in the acute care setting, this technique could be adapted for use during electrophysiologic studies where ventricular tachyarrhythmia is anticipated . Finally, the potential exists for a completely "automated" bedside unit connected to the defibrillating catheter capable of detecting and treating both bradyarrhythmia and ventricular tachyarrhythmia . Acknowledgment We are grateful to the staff of the University Hospital Coronary Care Unit for their assistance, University Hospital Instructional Resources for illustrations, and Suzanne Stewart for manuscript preparation .
References 1 . Dahl C, Ewy GA, Warner ED, Thomas ED . Myocardial necrosis from direct current countershock : effect of paddle electrode size and time interval between discharges . Circulation 1974 ;50 :956-961 . 2. Zipes DP, Jackman WM, Heger JJ, et al . Transvenous cardioversion of ventricular tachycardia and termination of ventricular fibrillation in man (abstr) . Am J Cardiol 1982 ;49 :1022 . . 3 Jackman WM, Zipes DP. Low energy synchronous cardioversion of ventricular tachycardia using a catheter electrode in a canine model of subacute myocardial infarction . Circulation 1982 ;66 :187-195 . 4. Mirowski M, Mower M, Slaewen WS, Tabatznlk B, Mendeloff Al . Standby automatic defibrillator . Arch Intern Mad 1970 ;126 :158-161 . 5 . Schuder JC, Sloeckle H, West JA, Keskar PY, Gold JH . Ventricular defibrillation in the dog with a bielectrode intravascular catheter . Arch Intern Med 1973 ; 132 :286-290 . 6 . Denniston RH, Mower M, Mirowski M . Automatic standby defibrillator (abstr) . J Assoc Adv Med Instrum 1971 ;5 :110 . 7 . Schuder JC, Stoeckle H, West JA, Keskar PY . Relationship between electrode geometry and effectiveness of ventricular defibrillation in the dog having one electrode in the right ventricle and other electrode in the superior vena cava or external jugular vein or both . Cardiovasc Res 1973 ;7 :629637 . 8 . Mirowski M . Implanted Defibrillators . Proceedings of Purdue Cardiac Defibrillation Conference, 1975 .
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