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528
What Is the Best Method for Assessing the
Long-term Outcome of Surgery for Accessory
Pathways and Atrioventricular Junctional
Reentrant Tachycardias?
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Lloyd M. Davis, MBBS, FRACP; David C. Johnson, MBBS, FRACS;
John B. Uther, MBBS, BSc(Med), MD, FRACP; Graham Nunn, MBBS, FRACS;
David A.B. Richards, MBBS, BSc(Med), MD, FRACP, FACC;
William Meldrum-Hanna, MBBS, FRACS; and David L. Ross, MBBS, FRACP, FACC
The success of surgery for supraventricular tachycardia (SVT) is evaluated by a variety of
methods in different hospitals. Unfortunately, the predictive values of these methods are not
known. We therefore compared the various methods in 261 patients undergoing surgery for SVT
at Westmead Hospital since 1981. Surgical outcome was assessed by early tests during the first
week after surgery (serial 12-lead electrocardiograms, telemetric monitoring of the electrocardiogram, and electrophysiological study performed using epicardial wires); later tests at 6
months after surgery (12-lead electrocardiograms and electrophysiological study); and symptomatic review done by telephone interview at a median of 34 months after surgery. Early tests
were obtained in 97%, later tests were obtained in 76%, and symptomatic review was obtained
in 98% of patients. All of the examined tests were inaccurate methods of surgical assessment
compared with the late electrophysiological study. A large proportion of the patients proven to
be surgical failures at the late electrophysiological study were not detected by early tests (83%),
by later electrocardiograms (66%), or by symptomatic assessment (41%). Accurate assessment
of surgical outcome requires a late electrophysiological study to permit comparison of surgical
techniques. Late electrophysiological study also provides accurate information on the current
risks and benefits of proposed surgery for communication to patients to enable them to make
an informed decision on future treatment. Most patients are willing to have a late electrophysiological study and usually benefit from clarification of their true surgical outcome. (Circulation
1991;83:528-535)
Surgical cure of tachycardias due to accessory
pathways and, more recently, atrioventricular
(AV nodal) junctional reentry has been attempted using a variety of operative techniques since
1967.1,2 Determination of the best surgical technique
and communication of the risks and benefits of
surgery to the patient require accurate assessment of
surgical outcome. To date, most reports have used
the results of operative mapping, early electrocardiography, and early electrophysiological study to judge
From the Cardiology Unit, Westmead Hospital, Westmead,
Australia.
Supported by National Heart Foundation grant PM100 (National Heart Foundation of Australia, Woden, A.C.T., Australia).
Address for reprints: Dr. D.L. Ross, Cardiology Unit, Westmead Hospital, Hawkesbury Road, Westmead, N.S.W., Australia,
2145.
Received July 3, 1990; revision accepted October 16, 1990.
operative outcome.1-34 However, the predictive value
of these tests for determining long-term outcome has
not been determined. Early studies may be inaccurate predictors of long-term outcome. Operative
trauma or perioperative edema around either the
accessory pathways or the AV node may transiently
inhibit function of the arrhythmia circuit and therefore masquerade as a surgical success at these early
tests. Symptomatic follow-up may also be an inaccurate method of surgical assessment because postoperative palpitations may be due to a variety of
arrhythmias other than that for which surgical cure
was attempted3 and surgical failures may be asymptomatic.
To determine the accuracy of current methods of
assessing surgical success or failure, we compared the
results of early studies done during the first week
after surgery (intraoperative electrophysiological
Davis et al Assessing Long-term Outcome of Surgery
study, telemetric monitoring of the electrocardiogram, serial 12-lead electrocardiograms, and electrophysiological study done using epicardial wires attached at surgery) with studies done 6 months after
surgery (12-lead electrocardiogram and electrophysiological study) in 261 patients who had surgery for
supraventricular tachycardia at our hospital since
1981. The correlation with symptoms on prolonged
follow-up was also assessed.
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Methods
We reviewed all 261 patients who underwent surgery for supraventricular tachycardia at our hospital
between October 1981 and February 1989. Surgical
dissection for AV and ventriculoatrial accessory
pathways was performed using the endocardial approach described by Sealy and Gallagher.4 Surgical
dissection for AV junctional reentrant tachycardia
(also known as AV nodal tachycardia) was performed using the technique we described.5,6 Patients
who had surgery for atrial tachycardias or tachycardias due to nodoventricular fibers were not included
in this analysis. Intraoperative mapping was performed using a hand-held probe using previously
described techniques.5,7 After the dissection, all patients had additional intraoperative electrophysiological assessment to confirm the initial success of
surgery. All patients had telemetric monitoring of the
electrocardiogram for at least 5 days after surgery
and had serial 12-lead electrocardiograms during the
week after surgery. The results of telemetric monitoring and the serial electrocardiograms in this period were grouped together for analysis and termed
"the early electrocardiogram." An electrophysiological study was performed 1 week after surgery, in the
drug-free state, using epicardial wires placed during
surgery.
A late, 6-month postoperative electrophysiological
study while off all antiarrhythmic agents was requested of all patients. Quadripolar electrodes were
positioned in the high right atrial appendage and the
right ventricular apex, and a tripolar catheter was
positioned at the His-bundle region. Unless there
was definite ventriculoatrial dissociation during this
study, a coronary sinus electrode was also inserted.
The stimulation protocol has been described.34
Briefly, it consisted of assessment of antegrade and
retrograde conduction by insertion of extrastimuli
after a stable drive train of eight beats. The initial
extrastimulus was introduced 550 msec after the
drive train and then at decreasing intervals to atrial
and ventricular refractoriness. AV and ventriculoatrial Wenckebach thresholds were also determined.
Repeated burst atrial and ventricular pacing close to
the Wenckebach thresholds was then performed in
an attempt to induce tachycardias. All patients who
had surgery for atrioventricular junctional reentrant
tachycardia were also assessed during intravenous
infusion of 5 ,ug/min isoprenaline and after 1 mg i.v.
atropine if no arrhythmia was inducible in the base-
529
line state. All induced arrhythmias were mapped in
detail.
A late electrocardiogram was also taken at the
time of admission for the 6-month postoperative
electrophysiological study.
The presence of any function of an attempted
accessory pathway, no matter how compromised,
either on the electrocardiogram or at the electrophysiological study was regarded as a surgical failure.
Accessory pathways located at different sites to those
attempted at surgery were not regarded as surgical
failures but rather defined as mapping failures. In
cases with AV junctional reentrant tachycardia, surgical failure was defined as the ability to induce three
or more beats of AV junctional reentrant tachycardia. Persistent dual AV nodal pathways and less than
three apparently AV junctional echo beats were not
regarded as surgical failures.
Patient follow-up was performed by telephone
interview using a standard questionnaire. The occurrence of rapid regular palpitations of sudden onset
and offset were regarded as symptomatic failures for
the purposes of analysis. Most of these palpitations
were not documented on an electrocardiogram and
may have been due to other arrhythmias, such as
sinus tachycardia and atrial flutter.
Statistical Analysis
Sensitivity, specificity, and predictive accuracy
were calculated using the results of the 6-month
postoperative electrophysiological study as the gold
standard for determining surgical success or failure.35
Results
Division of 214 accessory pathways was attempted
in 174 patients. One hundred twenty-one accessory
pathways (57%) were located in the left free wall, 68
(32%) in the posterior septal space, and 25 (11%) in
the right free wall. Thirty-nine percent of the 174
patients had a posterior septal pathway. A total of 39
patients had surgery for a combination of either left
free wall, right free wall, or posterior septal pathways
(one had surgery for accessory pathways in all of
these locations). An additional 91 patients had surgery for AV junctional reentrant tachycardia. Another four patients had surgery for both accessory
pathway and AV junctional reentrant tachycardia.
Indications for surgery in patients with an accessory
pathway were failed medical therapy in 71 patients
(41%), patient preference in 57 (33%), and potentially lethal rapid antegrade conduction over the
accessory pathway in 43 (25%). An additional three
patients had division of their accessory pathway as a
concurrent procedure to other cardiac surgery. In
patients having AV junctional reentrant tachycardia
surgery, the major indications were failed medical
therapy in 52 (57%) and patient preference in 30
(33%). An additional nine patients had surgery as an
adjunctive procedure to other cardiac surgery. The
median length of postoperative follow-up was 34
months (range, 5-90 months).
530
Circulation Vol 83, No 2 February 1991
TABLE 1. Number of Tests Performed
Atrioventricular
junctional
Accessory
reentrant
pathway
tachycardia
n
%
n
%
Early ECG
174
100
91
100
170
Early EPS
98
87
96
Late ECG
139
80
80
88
172
99
89
Symptom review
98
Late EPS
124
71
78
86
Early ECG, serial 12-lead electrocardiograms and electrocardiographic monitoring during the first week after surgery; EPS,
electrophysiological study.
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All evaluative procedures were requested in all
patients. Table 1 shows the number of tests that were
actually performed. Eight patients did not have an
early, 1-week postoperative electrophysiological
study because of intractable atrial fibrillation. A late
6-month postoperative electrophysiological study
was not obtained in 29% of patients with accessory
pathways and 14% of patients with AV junctional
reentrant tachycardia. Only four patients (2%) were
lost to follow-up.
The outcome of surgery as predicted by the various
evaluative tests is shown in Table 2. Early tests, either
the electrocardiogram, the electrophysiological
study, or a combination of both, predicted very low
surgical failure rates of only 2% for accessory pathways and 6% for AV junctional reentrant tachycardia
in keeping with other published results.1-34 Twelvelead electrocardiograms done during the first 6
months after surgery also predicted a low surgical
failure rate of 4% of accessory pathways and 9% for
AV junctional reentrant tachycardia. Long-term surgical failure rates, as detected by the 6-month postoperative electrophysiological study, were much
higher: 8% for accessory pathways and 24% for
patients with AV junctional reentrant tachycardia. In
all but one patient, long-term failures occurred in
patients with a posterior septal pathway or AV
TABLE 2. Apparent Surgical Failures Detected by Various Tests
Atrioventricular
junctional
Accessory
pathway
(n= 174)
n
%
Early ECG
Early EPS
Either early ECG or early EPS
4
3
4
5
25
10
2
2
2
4
15
8
reentrant
tachycardia
(n=91)
n
%
3
3
3
3
5
6
Late ECG
7
9
Regular palpitations
33
37
Late EPS
19
24
Early ECG, serial 12-lead electrocardiograms and electrocardiographic monitoring during the first week after surgery; EPS,
electrophysiological study; regular palpitations, symptoms suggestive of supraventricular tachycardia.
junctional reentrant tachycardia. Of the 10 accessory
pathway failures, six had inducible sustained tachycardia. Potentially lethal rapid antegrade conduction
over the accessory pathway was present in one of the
four patients without inducible tachycardia. Sustained tachycardia lasting at least 4 seconds was
induced in all of the failures with AV junctional
reentrant tachycardia; in 15 (79%) patients, it lasted
long enough to complete ventricular extrastimulus
testing. In addition to these surgical failures, there
also were six patients who had an additional arrhythmia circuit detected at a postoperative study that was
different than that attempted at initial surgery. In the
three mapping failures who had surgery for AV
junctional reentrant tachycardia, the undetected circuit was always the posterior type of this tachycardia.
The additional circuits in the three other mapping
failures who had surgery for an accessory pathway
consisted of another accessory pathway in two cases
and of anterior AV junctional reentrant tachycardia
in one case. Inclusion of these mapping failures in
the group of surgical failures did not significantly
change the sensitivity, specificity, and accuracy of the
examined tests.
Most patients (61%) had experienced palpitations
since surgery. For those who had accessory pathway
surgery, the palpitations were judged at interview to
be ectopic beats in 35 (37%), atrial flutter or fibrillation in 26 (28%), and sinus tachycardia in eight
(9%); in 25 patients (27%), the palpitations were
suggestive of supraventricular tachycardia (i.e., the
palpitations were rapid, regular in nature, and of
sudden onset and offset). For those who had surgery
for AV junctional tachycardia, the palpitations were
judged at interview to be ectopic beats in 14 (21%),
atrial flutter or fibrillation in 12 (18%), and sinus
tachycardia in nine (13%); in 33 patients (49%), the
palpitations were suggestive of supraventricular tachycardia. Most patients (227, or 88%) thought their
surgery was successful even if they were symptomatic
or had electrophysiological evidence of failure. The
patients' opinions of surgical outcome compared with
symptomatic and electrophysiologically determined
outcomes are shown in Table 3.
The detection of long-term electrophysiological
failures by the various tests is shown in Table 4. Early
tests were poor indicators of long-term outcome,
detecting only 20% of accessory pathway and 16%
AV junctional reentrant tachycardia failures. Similarly, the late electrocardiogram detected only 50%
of accessory pathway failures and 26% of AV junctional reentrant tachycardia failures. Rapid regular
palpitations were present in only 59% of long-term
electrophysiological failures. Patients were also poor
judges of surgical outcome (as determined by the
6-month postoperative electrophysiological study).
Only 20% of accessory pathway failures and 26% of
AV junctional reentrant tachycardia failures thought
their surgery was a failure, irrespective of whether
they experienced postoperative palpitations.
Davis et al Assessing Long-term Outcome of Surgery
531
TABLE 3. Patients' Opinions About the Outcome of Surgery in Those With Symptoms or Documented Failure
Atrioventricular junctional reentrant
tachycardia
Accessory pathways
Unsure
Failure
Success
Unsure
Failure
Success
(n)
n
n
(n)
(n)
(n)
%
n
n
%
3
7
61
20
33
3
4
72
18
25
Palpitations consistent with SVT
1
5
13
68
0
19
2
80
8
10
Late EPS failures
SVT, supraventricular tachycardia; EPS, electrophysiological study.
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The sensitivity, specificity, and predictive accuracies of the electrocardiogram, early electrophysiological study, and symptomatic review when the late
electrophysiological study was used as the gold standard are shown in Table 5. None of the examined
tests had a sensitivity of more than 0.74, and most
had a sensitivity of approximately 0.3 for detecting
long-term outcome as determined by the 6-month
postoperative electrophysiological study.
Patients were also asked whether they derived any
benefit from having a late postoperative electrophysiological study and whether they would, with hindsight, still have had the study if given a choice.
Eighty-one percent of the accessory pathway patients
TABLE 4. Number of Long-term Surgical Failures Detected by
Various Tests
Atrioventricular
junctional
Accessory
pathway
tachycardia
(n=10)
(n=19)
reentrant
n
%
n
%
1
5
20
2
Early ECG
13
10
2
1
Early EPS
20
3
16
2
Either early ECG or early EPS
50
5
26
5
Late ECG
74
14
30
3
Regular palpitations
32
60
6
6
EPS
ECG
and/or early
Any
Early ECG, serial 12-lead electrocardiograms and electrocardiographic monitoring during the first week after surgery; EPS,
electrophysiological study; regular palpitations, symptoms suggestive of supraventricular tachycardia.
and 65% of the AV junctional reentrant tachycardia
patients who had a late electrophysiological study felt
that the test had been helpful by providing clarification or reassurance about their surgical outcome.
Many of the patients who did not have a late electrophysiological study (21 of 50, or 42%, accessory
pathway patients and seven of 13, or 54%, AV
junctional reentrant tachycardia patients) also felt
that an electrophysiological study would have been
helpful to provide some reassurance or clarification
of their surgical outcome. With the benefit of hindsight, only 18 of the 172 accessory pathway patients
(10%) and 11 of the 89 AV junctional reentrant
tachycardia patients (12%) contacted would have
preferred to avoid a late electrophysiological study.
All of the remaining patients (except six patients who
were uncertain and four who were lost to follow-up)
would still have had a late electrophysiological study,
either for their own benefit or for research purposes.
Discussion
Several different surgical techniques are used for
curing accessory pathways and AV junctional reentrant tachycardia: endocardial versus epicardial approaches, cryoablation, and perinodal dissections of
different types.4,6,12,28,33 Extraordinarily high success
rates are claimed by some groups for their particular
approaches. Comparisons of the efficacy of the various techniques are hindered by variations in methods
of determining late outcome of the surgery. The
adequacy of the postoperative testing is likely to be a
major determinant of the reported success rates.
Electrophysiological testing just before hospital dis-
TABLE 5. Sensitivity, Specificity, and Accuracy of Various Tests Used for Evaluating Surgery for Supraventricular Tachycardia Compared
With Outcome Determined by a 6-Month Postoperative Electrophysiological Study
Atrioventricular junctional
reentrant tachycardia
Accessory pathways
Accuracy
Specificity
Sensitivity
Accuracy
Specificity
Sensitivity
0.74
0.96
0.05
0.93
0.99
0.20
ECG
Early
0.76
0.98
0.11
0.92
0.99
0.10
Early EPS
0.76
0.96
0.16
0.94
0.99
0.20
Early tests
0.79
0.97
0.26
0.97
1.00
0.50
Late ECG
0.79
0.96
0.32
0.96
0.99
0.60
Early EPS and any ECG
0.74
0.79
0.84
0.81
0.89
0.30
Regular palpitations
0.78
0.95
0.26
0.87
0.93
0.20
Patient opinion
first
week
after
the
surgery; EPS, electrophysEarly ECG, serial 12-lead electrocardiograms and electrocardiographic monitoring during
iological study; regular palpitations, palpitations suggestive of supraventricular tachycardia; patient opinion, patient opinion of whether
surgery was a success or failure.
532
Circulation Vol 83, No 2, February 1991
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charge is appealing but does not detect transient
abolition of accessory pathway function. This may
last several weeks. In addition, most patients dislike
detailed, four-catheter electrophysiological studies
only 1 week after major open-heart surgery. Hence,
limited electrophysiological studies are usually performed at that time using only percutaneous epicardial wires or a reduced number of endocardial electrodes without a coronary sinus catheter. These
minimize patient discomfort but are incomplete electrophysiological studies. Inducing the patient to return to the hospital for a comprehensive electrophysiological study several months after surgery also has
inherent problems. Often patients have travelled
long distances to referral centers and do not want to
return, may be unwilling to take additional time off
work, may not want to incur further expense, or may
find the thought of yet another electrophysiological
study distressing. Some cardiologists and surgeons
argue that postoperative symptoms are the gold
standard and that routine late invasive electrophysiological testing is expensive, dangerous, and irrelevant. We disagree. Symptoms may be misleading, are
often absent in surgical failures, and are often present in objective surgical successes. Placebo-type
responses occur with surgery at least as often as with
any other form of treatment. In our experience, most
asymptomatic patients with evidence of persistent
accessory pathway function or inducible tachycardia
at late electrophysiological study will develop symptoms if followed long enough. In addition, it is
important for the surgeon to know if the target
tissues were successfully divided so that individual
performances can be improved and the results from
different institutions can be compared objectively.
This quality control aspect is essential when arrhythmia surgery programs are begun, surgeons are in
training, or new surgeons join the staff.
Frequently Used Methods of Surgical Assessment
Most series have used operative mapping, electrocardiograms done during the first week after surgery,
and an electrophysiological study performed via epicardial wires at 1 week after the operation to evaluate surgery.1-29,33,34 Using these tests, high success
rates, approaching 100%, have been claimed for both
accessory pathway operations and those done for AV
junctional reentrant tachycardia.1-29,33,34 This was
also the case in our experience when the results of
early tests were used as the determinant of surgical
success (Table 2). However, late electrophysiological
study in our patients has demonstrated these early
studies to be poor predictors of long-term outcome,
detecting only 20% of accessory pathway and 16% of
AV junctional reentrant tachycardia failures.
As expected, late evaluation with the electrocardiogram is an inaccurate method of surgical assessment. Only accessory pathways with a visible delta
wave in sinus rhythm or supraventricular tachycardia
documented on an electrocardiogram will be detected. In our study, a late electrocardiogram de-
tected only 50% of the long-term electrophysiological
accessory pathway failures and 26% of the AV junctional reentrant tachycardia failures (Table 4).
More frequent Holter monitoring may have documented supraventricular tachycardia during symptoms. However, prolonged monitoring over weeks to
months would have been required in most cases. In
some of our patients, the first symptomatic episode of
tachycardia did not occur for as long as 6 months
after surgery. As a rule, patients do not like prolonged electrocardiographic monitoring. Furthermore, both symptomatic and asymptomatic patients
would need to be studied. Therefore, prolonged late
electrocardiographic monitoring is an expensive and
unrealistic option.
Assessment of Operative Outcome by Late
Electrophysiological Study
The late electrophysiological study 6 months after
surgery was the most accurate and sensitive method
of assessing surgical outcome. This was not unexpected as late assessment should detect surgical
failures who were missed by early postoperative tests
because of transient impairment of their accessory
pathway or arrhythmia circuit. The electrophysiological study will also detect arrhythmia circuits due to
AV junctional reentrant tachycardia and accessory
ventriculoatrial pathways. These will be missed by
the electrocardiogram or Holter monitor unless the
patient has supraventricular tachycardia (which may
be infrequent) at the time of the test. The electrophysiological study also has the advantage over other
methods of assessment of being able to accurately
characterize any residual arrhythmia circuit and thus
give the surgeon and electrophysiologist an accurate
reason as to why surgery failed. This is important if
mapping and surgical techniques are to be improved
in the future. The late electrophysiological study may
be inaccurate if the accessory pathway or arrhythmia
circuit is traumatized during catheter insertion transiently preventing pathway detection or if the stimulation protocol used is not aggressive enough to
induce tachycardia. This is an uncommon phenomenon in our experience. Only two patients (1%) have
had documented tachycardia after having had a
"normal" 6-month postoperative electrophysiological study representing a failure rate of 1% (sensitivity, 0.94; specificity, 0.99; and accuracy, 0.99). Inclusion of these two patients in the analysis as surgical
failures does not change the conclusion that the
6-month postoperative electrophysiological study is
the most accurate and sensitive method of detecting
surgical success or failure.
Symptomatic Assessment of Surgical Outcome
The relief of symptoms is one of the major aims of
surgery; therefore, ideally, the abolition of significant
symptoms should be one of the gold standards used
for evaluating surgery. However, palpitations of some
sort are experienced by most patients after surgery.
In our study, 61% of patients had experienced some
palpitation since surgery. Fischell and colleagues3
Davis et al Assessing Long-term Outcome of Surgery
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found that 49% of their 45 patients had experienced
some palpitation after surgery. Postoperative palpitations may be due to a variety of arrhythmias such
as ectopic beats, atrial fibrillation, atrial flutter, and
sinus tachycardia in addition to reentrant supraventricular arrhythmias. Therefore, decisions as to the
significance of undocumented palpitations require
clinical judgment and would not be expected to be
very accurate. If the definition of "palpitations" is
made more restrictive and more likely to represent
supraventricular tachycardia (e.g., the presence of
sustained rapid regular palpitations of sudden onset
and offset similar to the preoperative symptoms),
the history becomes a more reliable indicator of
surgical failure but still lacks sensitivity and specificity (Table 5). In our study, symptoms suggestive
of supraventricular tachycardia were present in 17
of the 29 surgical failures (59%) at late electrophysiological study and 25 of the 171 electrophysiologically proven cures (13%). Fischell et a13 also
showed the low specificity of palpitations suggestive
of supraventricular tachycardia. One of their two
symptomatic "failures" had sinus tachycardia recorded on Holter monitor during the palpitation.
The higher incidence of symptoms suggestive of
supraventricular tachycardia in our study compared
with that of Fischell et al's study3 (5%) may be due
to the type of follow-up. All of our reported symptomatic follow-up was obtained by direct questioning of patients by interviewers experienced in the
follow-up of arrhythmia patients. Fischell and colleagues obtained their data by telephone interview
with the patient in only 29 of the 44 patients that
they studied, the remainder of their data being
obtained from questionnaires, the local physician,
and patient charts. In our experience, these lack the
accuracy of direct patient interview. Symptoms are
also insensitive because not all surgical failures will
necessarily be symptomatic at the current length of
follow-up. In our study, 12 of the 29 surgical failures
(41%) at late electrophysiological study had not
experienced palpitations suggestive of supraventricular tachycardia at a median follow-up of 34
months. The patients' own assessments of surgical
outcome are also an inaccurate yardstick of true
surgical outcome. Often, patients do not want to
disappoint themselves or their physicians by admitting that their surgery may have been a failure. In
our study, 21 of the 29 failures (72%) detected at
electrophysiological study considered their surgery
to have been successful even if they had experienced palpitations suggestive of supraventricular
tachycardia.
The high incidence of palpitations consistent with
supraventricular tachycardia but not based on surgical failure indicates another role for a late electrophysiological study-patient reassurance. Of our patients, 151 (75%) felt that the 6-month postoperative
electrophysiological study had been worthwhile for
clarifying their outcome and providing a high degree
of reassurance that their arrhythmias would not
533
return. Such information is also useful for life insurance, job applications, and military personnel and
those wishing to obtain or renew commercial or
military aviation licenses.
Natural History of Early Surgical Failures
Of additional concern is the possibility that patients predicted to be failures at early testing will be
"cures" at later study because of the effects of
maturation of scar tissue on the arrhythmia circuit.
This would make the results of early studies less
specific. In our study, this was rare. Only two of the
early failures were found to be normal at late electrophysiological study. Therefore, our data support
treating early failures as true long-term failures with
early reoperation.
Clinical but Not Electrophysiological Success
Some may argue that our definition of surgical
failure is unnecessarily stringent. In our study, four of
the 10 accessory pathway failures did not have supraventricular tachycardia induced at the late electrophysiological study. However, in one of these, the
accessory pathway was still capable of dangerously
rapid conduction. In the patients who failed surgery
for AV junctional reentrant tachycardia, four of the
19 had induced tachycardias that lasted only a few
seconds. Longer episodes were not inducible, even
after isoproterenol and atropine. It may be argued
that surgery had modified the arrhythmia circuit in
these patients without ablating it, thereby resulting in
a symptomatic cure. Although these are clinically
useful results, they still indicate failure of the surgery
to ablate the intended circuit and demonstrate room
for improvement of surgical technique.
Role of Preoperative Electrophysiological Assessment
in the Long-term Outcome of Surgery
Our data also highlight another of the major
problems with arrhythmia surgery - the need for
accurate and detailed localization of the circuits
involved. The results of surgery can only be as good
as the accuracy of the electrophysiological assessments before surgical dissection. In our study, six of
a total of 35 unsuccessful operations (17%) were
the consequence of additional pathways or circuits
that became evident only after the original circuit
was ablated at surgery. This occurred despite great
pains to detect and localize additional pathways and
circuits at the preoperative and operative electrophysiological studies. These failures are due to the
inherent problems of mapping techniques as well as
the phenomenon of preferred arrhythmia circuits,
usually with shorter conduction times, which tend
to hide other arrhythmia circuits or pathways with
longer conduction times. The mapping failures in
patients with AV junctional reentrant tachycardia
in our study illustrate this. In all of these cases, the
undetected circuit was always the slower conducting
posterior type rather than the faster conducting
anterior type. Failed mapping may also be a conse-
534
Circulation Vol 83, No 2, February 1991
quence of trauma to the additional pathways. This
may transiently inhibit their function and prevent
their detection.
10.
Conclusions
A late postoperative
11.
electrophysiological study
provides the most accurate method of assessing surgery for supraventricular tachycardia. It is likely that
a similar late electrophysiological study will be the
best method for determining the success rates of
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other methods of ablation such as percutaneous
catheter electrical, laser, or radiofrequency ablation.
Other measures such as the electrocardiogram and
1-week postoperative epicardial wire electrophysiological study can be used as a rough guide but miss as
much as 40% of accessory pathway and 68% of AV
junctional reentrant tachycardia failures. Symptoms
are poor guides to outcome. Palpitations are common
after surgery and usually represent arrhythmias other
than supraventricular tachycardia. Patients are also
poor judges of surgical success or failure, detecting
only 24% of documented long-term surgical failures.
The 6-month postoperative electrophysiological
study is readily obtainable in the majority of patients
and provides valuable reassurance, even in the patients who have been surgically cured. Accurate
feedback to surgeons of their long-term results
should lead to improved success rates and objective
comparison of surgical techniques and results.
Acknowledgments
We wish to thank Mrs. Anita Watts and Mrs. Vicki
Eipper for their help in collecting the data.
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KEY WORDS * supraventricular tachycardia
atrioventricular node
* surgery
c
Downloaded from http://circ.ahajournals.org/ by guest on June 18, 2017
What is the best method for assessing the long-term outcome of surgery for accessory
pathways and atrioventricular junctional reentrant tachycardias?
L M Davis, D C Johnson, J B Uther, G Nunn, D A Richards, W Meldrum-Hanna and D L Ross
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Circulation. 1991;83:528-535
doi: 10.1161/01.CIR.83.2.528
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