Conversion of Supraventricular Tachyeardias
with Rapid Atrial Stimulation
By GEORGE S. VERGARA, M.D., FRANK J. HILDNER, M.D.,
CLYDE B. SCHOENFELD, M.D., ROGER P. JAVIER, M.D.,
LAWRENCE S. COHEN, M.D., AND PHILIP SAMET, M.D.
SUMMARY
Rapid atrial stimulation (RAS) is a technic useful for converting the rapid ventricular response of atrial tachycardia, atrial flutter, or junctional tachycardia to a slower
ventricular rate with normal sinus rhythm or atrial fibrillation. It is particularly useful
when alternate methods such
therapy
as
DC cardioversion, carotid sinus massage, and drug
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either ineffective or undesirable. It is safe in patients with digitalis intoxication, does not require general anesthesia, documents atrial rhythm, and can be used
repetitively without cumulative effects.
RAS was performed 129 times in 87 patients (45 males; 42 females) whose ages
ranged from 33 to 90 years (mean 67 years). There were no major complications.
Overall, including both initial and repeat attempts, RAS successfully converted supraventricular tachycardia in 71% of cases and failed in 29%.
are
Additional Indexing Words:
Atrial arrhythmias
Digitalis intoxication
Atrial pacing
DC cairdioversion
S UPRAVENTRICULAR tachyeardias (SVT)
may produce serious hemodynamic alterations, particularly in patients with
underlying heart disease. When carotid sinus
massage and drug therapy are ineffective,
external DC cardioversion has been useful.1-5
External cardioversion, however, can be followed by significant complications in patients
who are digitalis intoxicated',10 who are too
ill to tolerate the anesthesia, or who exhibit
repeated episodes of SVT. Rapid atrial stimulation (RAS) offers an alternate method for
the treatment of SVT other than atrial
fibrillation (AF). It has been shown to be safe
in patients with digitalis intoxication, does not
Cardiac catheterization
require general anesthesia, is simple to perform, and can be used repetitively.11-'7 The
purpose of this paper is to describe the
indications for and results of RAS as a mode
of therapy in a large series of patients.
Materials and Methods
RAS was performed 129 times in 87 patients
(45 males; 42 females) who exhibited SVT other
than AF. The ages ranged from 33 to 90 years
with a mean age of 67 years. All but seven
patients were under treatment with digitalis, and
20 were also receiving either quinidine or
procaine amide hydrochloride (Pronestyl) prior
to the procedure. Of the 80 patients on digitalis,
31 were considered to be digitalis intoxicated.
The other 49 exhibited no apparent ill effects or
signs suggestive of intoxication.
The patients reported in this study represent
our experience with RAS over a 3-year period.
They are divided into three groups based on the
supraventricular rhythm found by surface ECG
and frequently on intraatrial electrode examination also. Those with atrial flutter (AFI) had
atrial rates of 240 beats/min or more, and
electrocardiographic appearances which included
a sawtooth baseline and usually some degree of
From the Division of Cardiology, Department of
Internal Medicine, Mount Sinai Medical Center,
Miami Beach, Florida, and the University of Miami
School of Medicine, Coral Gables, Florida.
Address for reprints: Frank J. Hildner, M.D.,
Mount Sinai Medical Center, 4300 Alton Road, Miami
Beach, Florida 33140.
Received January 13, 1972; revision accepted for
publication June 6, 1972.
788
Circulation, Volume XLVI, October 1972
SUPRAVENTRICULAR TACHYCARDIAS
atrioventricular (A-V) block. Those with
paroxysmal atrial tachycardia (PAT) had atrial
rates below 240 beats/min and usually recognizable P waves. The third group consisted of
patients with junctional tachycardia (JT) in
which the QRS complex of the ECG was not
preceded by a P wave and in some cases was
associated with retrograde P waves.
Of the 49 patients with AFI, 33 had
arteriosclerotic heart disease (ASHD), six had
rheumatic heart disease (RHD), three had
had
one
congenital heart disease (CHD
primary myocardopathy, and six had
no
obvious
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heart disease other than recurrent tachycardias.
Of the 34 patients with PAT, 23 had ASHD, six
had RHD, one had CHD, and four had no
obvious heart disease other than recurrent
tachyeardias. Of the four patients with JT, two
had ASHD and two had RHD.
Method of RAS
A SF Goetz pacing catheter with tip electrodes
1 cm apart was placed in the right atrium (RA)
transvenously, either through a percutaneous
puncture of a femoral vein or through a surgically
exposed antecubital vein. Under fluoroscopic and
electrographic control, the tip of the catheter was
usually placed at the RA-superior vena cava
junction or against the free wall of right atrium in
the upper portion of the chamber. All the
equipment was properly grounded.10 The cardiac
rhythm was analyzed using intraatrial electrodes
to record a right intraatrial unipolar and bipolar
electrogram.1820 Either a Medtronic* paired
pulse generator model 5837 or a Cordis
Synchrocor IIt modified to deliver 1200
stimuli/min and up to 25 ma was employed for
RAS. The right atrium was stimulated initially at
a rate slightly faster than the underlying initial
atrial rate. Pacing current was increased from 5
ma initially to 25 ma when necessary. RAS was
continued 15-30 sec after atrial capture was
assured. If a change in atrial rhythm was not
achieved, both the frequency of stimulation and
the current were increased by increments of
200/min and 5 ma, respectively, to a maximum of
1200 stimuli/min and 25 ma. If the right atrium
could not be captured at any level of ma, the
pacemaker catheter was repositioned until capture could be achieved. No optimum stimulation
frequency or ma was noted. In all but 10 patients,
the pacing catheter was left in the right atrium
after RAS until the patient's condition stabilized.
*Medtronic Inc., Minneapolis, Minnesota.
tCordis Company, Miami, Florida.
Circulation, Volume XLVI, October 1972
789
Table 1
Rapid Atrial Stimulation: Attempted Conversion
of Supraventricular Tachycardia*
Results
Attempt
Failure
Successful
Initial
Repeat
Total
N
%
84
8
92
75
47
71
N
28
9
37
%
25
53
29
*This table summarizes the overall results of RAS
conversion of atrial arrhythmias other than fibrillation.
Repeated attempts were performed 24 hours after the
initial attempt.
Results
Final Results
Conversion of SVT by RAS was successful
in 92 (71%) of 129 attempts and unsuccessful
in 37 (29%). These overall results are derived
from the combined data of (1) initial
conversion and (2) repeat conversion (table
1).
Initial Conversion. When RAS was performed for the first time in a given patient, all
attempts that converted AFI, PAT, or JT to
either normal sinus rhythm (NSR) or AF for
more than 24 hours were considered successful. All initial attempts in which RAS was
unable to change the original SVT in any
manner were considered failures. Conversion
was successful in 84 (75%) of 112 initial
attempts and was unsuccessful in 28 (25%). At
the end of the RAS procedure, conversion to
stable NSR was found in 42 attempts and
conversion to AF in 42 attempts. Of the 42
conversions to AF, 25 further converted
spontaneously to NSR within 24 hours and 17
others remained in AF (fig. 1).
Repeat Conversion. In 17 other instances,
RAS converted the original SVT to NSR or
AF, but within 30 min the rhythm reverted
back to the original SVT. All 17 patients were
given additional digitalis. When RAS was
repeated after 24 hours, eight (47%) converted
to stable NSR or AF, but nine (53%) remained
unchanged or reverted within 30 min again.
These 17 cases were classified as a different
group. After the initial attempt at RAS, the
VERGARA ET AL.
790
SVT was converted but did not remain so.
Because the SVT converted initially, these
attempts were not considered total failures,
but because the SVT did not remain converted neither were they totally successful. With
the use of additional digitalis and repeat RAS
after 24 hours, eight of these 17 cases were
successfully reconverted (fig. 1).
Atrial Flutter
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There were 68 attempts of RAS conversion
in 49 patients with AFl (fig. 2). Conversion
was initially successful in 48 but failed in 12.
Of the successful conversions, 21 converted
immediately to NSR, and 27 to AF. Of those
that converted to AF, 16 ultimately converted
further to NSR while 11 remained in AF.
Twelve initial attempts at RAS conversion
failed. After initial conversion to NSR or AF,
the rhythm in eight different patients reverted
to the original SVT. Repeated RAS after 24
hours resulted in stable NSR or AF in four
and failed in four. Twelve of the 49 patients in
this group required RAS more than once
during each hospitalization. The average
ventricular rate before RAS was 143
beats/min. Following conversion to stable
NSR or AF, the average ventricular rate was
91 beats/min.
RAS Conversion of Supraventricular Tachycordia
Total
NSR
in
Paroxysmal Atrial Tachycardia
There were 56 attempts of RAS conversion
in 34 patients with PAT (fig. 3). Conversion
was initially successful in 33 but failed in 15.
Of the successful conversions, 18 converted
directly to NSR and 15 converted to AF. Of
the 15 that converted to AF, nine converted
spontaneously to NSR and six remained in AF.
After conversion, the rhythm of eight patients
reverted to SVT. When RAS was repeated
after 24 hours in these eight, three converted
successfully to either NSR or AF and five
failed. Fifteen of the patients in this group
required RAS more than once during hospitalization. The average ventricular rate prior to
conversion was 140 beats/min. Following
conversion to stable NSR or AF, the average
ventricular rate was 98 beats/min.
Junctional Tachycardia
In the group of patients with JT, five
atternpts at RAS conversion were performed
in four subjects (fig. 4). Three initial attempts
were successful and one failed. All three that
succeeded converted directly to NSR. The
single attempt that reverted to JT after
conversion was successfully converted after
repeat RAS at 24 hours. One patient in this
group required repeat RAS. The average
ventricular rate before conversion was 132 and
after conversion, 83 beats/min.
itialI- 67
RAS Conversion of Atrial Flutter
125 via AF)
Repeot- 3
71%
Stable NSR-- 21
Total
RAS Conversion
Total Attempts
(129)
AF
tnitialRepeat-
17
To NSR
5
Reverted to AFI- 2 (1)
Directly
Stable NSR- 16
Total
Failure
Initial-28 1
Repeat- 9 | 29%
AFI
68 Attemps\
Figure
To AF
68
Atternp
11
Reverted to AFI- 6(3)
1
Results of RAS in all types of supraventricular tachycardia (SVT). Successful and unsuccessful conversions
to either NSR or AF occurred in both initial and repeated attempts (see text). When SVT converted to
normal sinus rhythm (NSR) or atrial fibrillation (AF)
the attempts were considered successful. Attempts in
which the SVT would not change to or could not be
maintained in either NSR or AF were considered
initial or repeated failucres.
Stable AF
s
Failed- 12
Figure 2
Results of initial RAS in episodes of atrial flutter
(AF1I. After successful conversion to either NSR or
AF, several cases reverted back to atrial flutter and
underwent RAS 24 hours later. Values in parentheses
indicate number of successful repeat RAS attempts
after 24 hours. See text.
Circulation, Volume XLVI, October 1972
SUPRAVENTRICULAR TACHYCARDIAS
RAS Conversion of Paroxysmal Atrial Tachycardia
Stable NSR-
18
Reverted to PAT- 2(1)
To NSR
Directly
To NSR
PAT
56 Attempt\
To AF
Failed
Stable AF
Reverted to
9
6
PAT- 6(2)
- 15
Figure 3
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Results of initial RAS in episodes of atrial tachycardia.
After successful conversion to either NSR or AF,
several cases reverted back to atrial tachycardia. Values
in parentheses indicate number of successful repeat
RAS attempts after 24 hours. See text.
Digitalis and RAS
Of the 87 total patients, 38 developed AF
with a rapid ventricular response after RAS.
The ventricular rate at this time was usually
10-40 beats/min less than during the SVT. This
finding was of interest because before conversion 15 of 38 exhibited signs such as anorexia,
nausea, premature ventricular contractions, or
PAT with block, which are usually associated
with digitalis intoxication.
In 17 patients after RAS, the rhythm
converted momentarily to NSR or AF with a
fast ventricular response and then reverted to
the original SVT. In these cases, a catheter
was left in the right atrium and more digitalis
was given. After 24 hours, RAS was repeated
RAS Conversion of Junctional Tachycardia
Stable NSR- 3
To NSR
Directly
JT
Reverted- 1(1)
AF-O
5 Attempts
Failed- 1
Figure 4
Results of initial RAS in episodes of junctional tachycardia. After successful conversion to either NSR or
AF, several cases reverted back to junctional tachycardia. Values in parentheses indicate number of successful repeat RAS attempts after 24 hours. See text.
Circulation, Volume XLVI, October 1972
791
and in eight cases conversion to NSR or AF
occurred easily and remained stable. A fast
ventricular rate after RAS suggested underdigitalization and in such cases digitalis was
given to slow the ventricular rate. Digitalis
was withheld after RAS if the ventricular rate
after conversion was slow.
Complications
There were no fatalities or major complications following RAS. Three patients converted
to NSR with first-degree heart block and
premature ventricular contractions which
were controlled with antiarrhythmic agents.
Sinus bradycardia or AF with slow ventricular
response occurred in 15 cases. In none of these
patients did the ventricular rate fall below 50
beats/min. Two other patients developed
sinus arrest, and both were controlled by
temporary pacing of the right atrium. Seven of
the patients, who had AFl had sick sinus
node21, 22 syndrome, eventually requiring permanent pacemakers.
Discussion
Several theories have been proposed to
explain the mechanisms of SVT. Previous
studies have shown that AFI may be caused
by an atrial circus mechanism23-25 or by an
ectopic atrial pacemaker firing at a rapid
rate.26 Other studies have shown that SVT
results from a reentry phenomenon, involving
the atrium and A-V junctional area.27-31 Based
on these theories, several mechanisms have
been proposed to explain how SVT responds
to RAS therapy. One mechanism involves
overdrive suppression of an ectopic atrial
focus.11' 82, 33 Another mechanism involves
production of atrial diastolic depolarization by
single or multiple atrial stimuli delivered at
the appropriate time within the cardiac cycle.
In this way, interruption of the reciprocating
circus mechanism allows NSR to resume.27' 28
The third mechanism involves delivery of
atrial stimuli to produce AF.34 During both
RAS and AF, concealed conduction at the
level of the A-V node results in slowing the
ventricular rate. Experience has shown that the
AF induced by RAS is often an unstable
VERGARA ET AL.
792
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rhythm which may spontaneously convert to
NSR.14 15
The most serious potential complication
following RAS is the accidental stimulation of
the right ventricle, which would probably
produce ventricular tachycardia or fibrillation.
This did not happen in the present series.
Nevertheless, we feel that it is imperative that
the catheter be positioned under electrographic and fluoroscopic control with the tip of the
catheter placed in such a position that it
cannot be deflected into the ventricle. Several
minor complications did occur. In three
patients, RAS was followed by ventricular
premature contractions (VPCs), which were
readily controlled with medication. Two patients had asystole, lasting up to 10 sec
immediately after RAS was stopped. This
situation is easily controlled by pacing the
right atrium or the right ventricle with the
same electrode catheter. This is a convenient
method of controlling bradycardia, following
conversion of SVT to NSR, and is an
advantage of the RAS method not available
with DC cardioversion.
RAS is an effective method for slowing the
ventricular rate in patients with SVT. It
enables conversion of AFI, PAT, or JT to
slower NSR or AF without the necessity of
general anesthesia. RAS is an alternative
method to DC cardioversion for slowing the
ventricular rate in patients with recurrent SVT
who require repeated conversion and particularly in patients with suspected digitalis
intoxication.
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Conversion of Supraventricular Tachyeardias with Rapid Atrial Stimulation
GEORGE S. VERGARA, FRANK J. HILDNER, CLYDE B. SCHOENFELD,
ROGER P. JAVIER, LAWRENCE S. COHEN and PHILIP SAMET
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Circulation. 1972;46:788-793
doi: 10.1161/01.CIR.46.4.788
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