Electrophysiological abnormalities before and after surgery for atrial septal defect

Journal

of Electrocardiology

Vol. 26 No. 3 1993

Electrophysiological Abnormalities Before and After Surgery for Atria1 Septal Defect

Yoshio Kano, MD, Toshio Abe, MD, Minor-u Tanaka, and Eiji Takeuchi, MD

MD,

Abstract: The authors evaluated the electrophysiological parameters, atrial-His interval, His-ventricular interval, Wenckebach cycle length, corrected sinus node recovery time (CSNRT), and sinoatrial conduction time (SACT) before and after operation in 28 children with atria1 septal defect (ASD). Before operation, electrophysiological abnormalities were detected in 20 (79%) of the 28 patients. Preoperative comparison of the mean value in each parameter between the two age groups showed higher values in all parameters in the older group. In 17 patients who underwent operation, atrial-His interval, Wenckebach cycle length, CSNRT, and atria1 effective refractory period (AERP) significantly decreased after operation; preoperatively abnormal Wenckebach cycle length, CSNRT, and AERP values were normalized in many of them. Thus, electrophysiological abnormalities were already present before operation in the ASD children and were severer in the older children, but were improved to some degree following operation. Key words: atria1 septal defect, conduction system, arrhythmia, electrophysiological study.

Supraventricular

arrhythmias

such

tal (Nagoya, Japan) between May 1984 and October 1986, 28 ( 10 boys and 18 girls) were entered into this study. Their ages ranged from 2 to 16 years (mean, 9.2 years). We adequately explained to the patients and their parents the purpose (purely investigative in nature) and content of this electrophysiological study and obtained their informed consent to perform the study before and after operation. Twenty-six patients had ostium secundum defect and the other two had sinus venous defect. Mild pulmonary valve stenosis and patent left superior vena cava were observed in one patient each. Of the 28 patients, 2 1 underwent operation during this study. A postoperative electrophysiological study was not performed in four patients due to slight postoperative impairment of liver function in two cases and parental refusal in two cases. The remaining 17 patients (mean age, 9.1 years) did undergo an electrophysiological study after operation. The interval between the preoperative electrophysiological study and operation varied from 8 to 349 days (mean, 92 days), and the interval between operation and the

as atria1 fibril-

syndrome are sometimes observed after operation for atria1 septal defect (ASD),‘-’ and they have been attributed to surgical insult to the conduction system.3-7 However, recent electrophysiological studies before and after operation for ASD have suggested the involvement of ASD itself in the dysfunction of the conduction system.8-14 We performed electrophysiological studies in 28 children with ASD and evaluated preoperative abnormalities, the effects of age, and changes after operation. lation

and

sick

sinus

Materials

and Methods

Of the 35 patients with ASD who underwent preoperative cardiac catheterization at the Meijo HospiFrom the Department of Thoracic Surgery, Nagoya lJniver$ty School of Medicine, Nagoya, Japan. Reprint requests: Yoshio Kano, MD, Department of Cardiovascular Surgery, Meijo Hospital, 1-3-1, Sannomaru, Naka-ku, Nagoya, 460 Japan.

225

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Journal of Electrocardiology

Vol. 26 No. 3 July 1993

Table 1. Electrophysiological Parameters (Mean +- SD) Prior to Atria1 Septal Defect Repair Mean * SD Basal cycle length Atrial-His interval His-ventricular interval Wenckebach cycle length Sinoatrial conduction time* Corrected sinus node recovery time Atria1 effective refractory period *Only data on 2 1 patients in whom could be obtained are shown.

662 93 43 424 199 341 222 sinoatrial

2 t ? 5 2 f 2

conduction

2.

Preoperative Abnormalities

131 20 6

135 57 116 41 time

postoperative electrophysiological study varied from 17 to 184 days (mean, 41 days). studies were performed Electrophysiological under local anesthesia in the six older children and under general anesthesia in the others using the same anesthetic method before and after operation in each child. All catheters were inserted via the femoral vein. A bipolar catheter was placed at the high right atrium for pacing and a tripolar catheter was placed at the tricuspid orifice for the recording of His-bundle electrograms. His-bundle electrograms were recorded by a modified method of Scherlag et a1.,15 and basal cycle length, atrial-His interval, and Hisventricular interval were measured. Corrected sinus node recovery time (CSNRT), sinoatrial conduction time (SACT), Wenckebach cycle length, which is the maximum atria1 pacing cycle length that does not induce Wenckebach type grade 2 atrioventricular block, and atria1 effective refractory period (AERP) were measured by programmed pacing and premature stimulation (stimulation width, 1.O ms; voltage, 3.5 V). Sinoatrial conduction time was obtained by Strauss’ method16 and expressed as the total SACT. When 1: 1 conduction was observed, even at a pacing rate less than 300 ms, further measurements were not performed in some patients, and the maximum pacing cycle length used was substituted for Wenckebath cycle length. Table

Results

The mean value + SD in each parameter in the 28 patients preoperatively examined before surgery is shown in Table 1 and the detection rate of abnormal values is shown in Table 2. Values that were more than twice the standard deviation of the previously reported normal values’7-2o were regarded as abnormal. Electrophysiological abnormalities were present before operation in 22 (79%) of the 28 patients (Table 2). Wenckebach cycle length, SACT, and CSNRT were abnormal in more than 50% of the patients; atrial-His interval, His-ventricular interval, Wenckebach cycle length, SACT, CSNRT, and AERP were abnormal in some patients (Table 2). The electrophysiological parameters were classified as those at the sinus node, right atrium and the atrioventricular node, and the detection rates of abnormal values were compared among these sites. The detection rate of abnormal values was highest at the sinus node followed by the atrioventricular node and right atrium, respectively (Table 3). The range of the systemic pulmonary flow ratio (Qp/Qs) in our subjects was from 2.1 to 2.6. The correlation coefficient between the systemic pulmonary flow ratio (Qp/Qs) and each parameter was calculated, but no significant correlation was observed.

Effects of Age The 28 patients examined before surgery were classified into two age groups: the younger group ._ _. (range, 2-9 years; n = 14) and the older group (range, lo-16 years; n = 14). The mean values + SD and the rates of abnormal values in each parameter were compared between these groups (Tables 2

Frequency of Abnormal Electrophysiological Parameters Prior to Atria1 Septal Defect Repair

Atrial-His interval His-ventricular interval Wenckebach cycle length Sinoatrial conduction time* Corrected sinus node recovery time Atria1 effective refractory period More than one item

Younger Children (n = 14)

Older Children (n = 14)

All Children (n = 28)

No. (%)

No. (%)

No. (%)

6 2 12 9 13 6 13

7 2 lb 11 18 8 22

1 0 4 2 5 2 10

(7) (0) (29) (17) (36) (14) (71)

*Only data on 12 younger children and 9 older children tUpper limits reported by Levin,” Kugler,18 Krongrad,19

(43) (17) (86) (90) (93) (43) (93)

in whom sinoatrial conduction and DuBrowZo were used.

time could

(25) (7) (57) (52) (64)

(29) (79)

be obtained

Upper Normal Limit+ < 104’7 <51’7 <37519 <200’S <275” <24520

are shown.

Electrophysiological Table 3. Frequency of Abnormal Electrophysiological Parameters Prior to Atria1 Septal Defect Repair Number of Abnormal Patients

Abnormal Rate (“A)

18 8 16

64 29 57

Sinus node Right atrium Atrioventricular

node

and 4, respectively).

The older group showed higher mean values (nonpaired t-test) and detection rates of abnormal values in all parameters than the younger group.

Postoperative Changes

In 17 patients in whom both pre- and postoperative electrophysiological studies were performed, changes after operation were evaluated. Figure 1 shows pre- and postoperative values in each parameter in the two age groups. Atrial-His interval, Wenckebach cycle length, CSNRT, and AERP significantly decreased after operation (P -=c.05, paired t-test), but basal cycle length, His-ventricular interval, and SACT did not differ before and after operation. Preoperative abnormal values were normalized after operation in some patients; Wenckebach cycle length was normalized in three of eight patients, CSNRT in five of nine, and AERP in all five (Fig. 1). Measurement of SACT was impossible because the plateau line could not be drawn in 7 of the 17 patients before operation but only in 2 after operation.

Table 4. Electrophysiological Parameters (Mean 5 SD) in Younger and Older Children Younger Children (n = 14; range, 2-9 years) Basal cycle length* Atrial-His interval* His-ventricular interval* Wenckebach cycle length* Sinoatrial conduction time+ Corrected sinus node recovery time* Atria1 effective refractory period+

589 ? 93 82 ? 14 40 r+_4 347

* 94

163 % 34 277 2032

Older Children (n = 14; range, lo-16 years) 735 ? 124 103 * 19 46 2 7 502 ? 247

127

2 42

2 84

406

?

110

31

241

2 43

*P < .Ol tOnly data on 12 younger children and 9 older children in whom sinoatrial conduction time could be obtained are shown. *P < .05 (by nonpaired t-test).

Abnormalities

of ASD

l

Kano et al.

227

Discussion

Many electrophysiological studies have been permostly those with congeniformed in children,‘7-‘3 tal heart disease. On the other hand, atrial-His interval and His-ventricular interval in normal children have been reported,17 but not other parameters. Actual normal values might be lower than the values used in this study. However, we considered that the detection rates of abnormalities are not, at least overestimated using these normal values. Reports have shown considerable high detection rates of preoperative electrophysiological abnormalities in ASD children,8-‘4 which were supported by our results. Clark et al.’ reported a correlation between electrophysiological abnormalities and Qp/Qs, but such correlation was not observed in this study. This may have been caused by the small deviation in Qp/Qs (range, 2.1-2.6) in our subjects. Ruschhaupt et a1.9 observed preoperative electrophysiological abnormalities in 8 of 2 1 ASD children aged 2.5 years or older, but none in 34 ASD children aged less than 2.5 years, suggesting that age is an important factor associated with preoperative electrophysiological abnormalities. In our study, significant differences were observed in all parameters between the older and younger groups, also strongly suggesting the effects of age. Shiku et al. ‘” provided more accurate data on the significant prolongation in PA, His-ventricular, and PR intervals with age in ASD children using normal children as controls. The mean value in each item and the detection rate of abnormal values were similar between 6 of the 14 older children examined under local anesthesia and in the other 8 children examined under general anesthesia. These findings suggest no effects of anesthesia on electrophysiological evaluation. Bolens et al.” reported significant postoperative decreases in the same parameters as ours in 18 ASD children (mean age, 10 years). Though similar results were obtained in our study, SACT and His-ventricular interval did not significantly decrease after operation. However, the number of patients in whom measurement of SACT was impossible markedly decreased after operation. Kugler et al.” considered that impossibility of SACT measurement represents entrance block into the sinus node and decreased sinus node function. Based on their theory, SACT may also tend to improve after operation. Bagger et aLI3 found no changes in the PA and atrial-His intervals, SACT, and AERP, and prolongation in CSNRT and His-ventricular interval in adult patients (mean age, 32 years). This suggests that postoperative im-

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Journal of Electrocardiology

Vol. 26 No. 3 July 1993

600 16C

55

800

140

50

700

120

45

900

\

600

40

500 Fig. 1. Postoperative

changes in electrophysiology parameters. (A) basal cycle length; (B) atrial-His interval; (C) His-ventricular interval; (D) Wenckebach cycle length; (E) sinoatrial conduction time; (F) corrected sinus node recovery time; (G) atria1 effective refractory perod. (B, D, F, G) Significant by paired t-test (P < .05). The broken lines indicate normal upper limits. 0 = younger group; 0 = older group.

80

_ pre. A

post.

35

pre.

post.

pre.

B

post.

C

a

pre.

post.

D

600

300

500

250

------__

200 150

- 400

250

100

pre.

post.

E

provement in electrophysiological abnormalities becomes difficult with age. Thus, electrophysiological abnormalities were present before surgery in the ASD children, aggravated with age, but improved to some extent by operation. We speculated that these serial changes are associated with the presence and duration of the left to right shunt at the atria1 level. Therefore, ASD repair at earlier ages may be useful for preventing electrophysiological abnormalities. None of our subjects had arrhythmia. Further studies are needed on whether subclinical electrophysiological abnormalities are useful for predicting the occurrence of arrhythmia late after operation.

pre. F

post.

pre.

post

G

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