New Q waves after bypass grafting: Correlations between graft patency, ventriculogram and surgical venting technique

J. ELECTROCARDIOLOGY, 9 (4) 1976 321-327

New Q Waves After Bypass Grafting: Correlations Between Graft Patency, Ventriculogram and Surgical Venting Technique BY AGOP AINTABLIAN, M.D., ROBERT I. HAMBY, M.D., IRWIN HOFFMAN, M.D., MARVIN L. HARTSTEIN, M.D. AND B. GEORGE WISOFF, M.D.

SUMMARY

varied. They include ventricular trauma and conduction delays resulting from surgery or venting, as well as infarction. This may be due to compromised arterial inflow either in nonoperated vessels or in the vessels distal to the anastomosis with patent grafts, or due to occluded grafts.

New Q waves were observed in 35 (11%) of 321 patients u n d e r g o i n g s a p h e n o u s vein bypass grafting with an overall mortality rate of 1.1%. Twenty-eight (80%) had postoperative arteriograms and ventriculograms and are reported. Ventricular venting was used intra-operatively in 17 patients and atrial venting in 11. The incidence of new Q wave was 22% in patients with ventricular venting and 5.5% in those with atrial venting (p<0.05). Complete or i n c o m p l e t e revascularization did not affect the incidence of new Q waves. New Q waves appeared in a zone of myocardium supplied by a grafted artery in all except two patients with ventricular venting in w h o m Q waves occurred within the zone of myocardium supplied by diseased ungrafted vessels. In the ventricular venting group, seven (41%) d e m o n s t r a t e d an improved or unchanged postoperative ventriculogram and ten (59%) had deteriorated ventriculograms. In 11 patients with atrial venting, nine (82%) s h o w e d i m p r o v e d or u n c h a n g e d p o s t operative ventriculograms and two (18%) had deteriorated ventriculograms. Ventricular venting patients with improved or unchanged postoperative ventriculograms had 7% graft closure as compared to 5% of those with atrial venting (pNS). Graft closure rate was 44% in ventricular venting and 20% (pNS) of patients with atrial venting who had deteriorated left ventriculograms. These findings indicate poor correlation between new Q waves and graft closure. Improved postoperative ventriculograms correlated well with graft patency despite new Q waves. The etiology of new post bypass graft Q waves are

New postoperative electrocardiographic Q waves have been described in 8 to 40% of patients undergoing bypass grafting for coronary a r t e r y disease. 1-5 Various theories have been p r o p o s e d , i n c l u d i n g g r a f t c l o s u r e , 6 int raoperat i ve myocardial t r a u m a v,s and even improved myocardial function in a ventricular segment opposite to a previously electrocardiographically "silent" infarct. 9 We report h e r e i n our experience with posto p e r a t i v e Q w a v e s in p a t i e n t s w i t h v e i n grafts and the relationship of new Q waves to v e n t r i c u l a r venting, graft patency and vent ri cul ar function.

MATERIALS AND METHODS Between December 1970 and January 1973, 350 patients underwent coronary bypass surgery. Twenty-nine patients were excluded because they also underwent partial ventricular resection or prosthetic valve replacement, together with aortocoronary bypass surgery. In the remaining 321, 35 patients developed new Q waves, making up the case material for the present study. All patients had preoperative left and right heart catheterization and left ventricular and coronary angiography using the Sones or Judkin's technique. Post-bypass recatheterization and angiography were done 10-15 days after operation, just before hospital discharge, in order to assess the patency of the grafts, as well as any change in left ventricular function as previously described (10,11). All angiograms and electrocardiograms (EKGs) were reviewed by two different cardiologists in order to compare pre- and postoperative studies. Electrocardiographic criteria for selection were limited to significant new Q waves. The Q wave criteria used to evaluate the EKG was essentially class 1-1 and 1-2 of the Minnesota code reported by Blackburn and associates (12). Cases presenting t r a n s i e n t ST segment or T wave changes without pathologic Q waves were excluded from this study. Eighty of 321 patients were operated upon for preinfarction angina, while 241 had elective surgery for angina. The patients were di-

From the Department of Medicine, Cardiology Division, and the Department of Surgery, Cardiovascular Division, Long Island Jewish-Hillside Medical Center, New Hyde Park, New York; Queens Hospital Center Affiliation, Jamaica, New York; and The School of Medicine, Health Sciences Center, State University of New York at Stony Brook, New York. Reprint requests to: Agop Aintablian, M.D., Cardiology Division, Long Island Jewish-Hillside Medical Center, New Hyde Park, NY 11040. 321

322

A I N T A B L I A N ET AL

vided into groups according to the technique used to vent the left ventricle during surgery. In patients with ventricular venting, the vent was inserted via the apex into the left ventricular chamber, whereas in patients with atrial venting, the vent was inserted into the left ventricle via one of the pulmonary veins. Group A comprised 104 patients with left ventricular venting and Group B comprised 217 patients with left atrial venting. Twenty-three new Q waves occurred in Group A and 12 in Group B. Of these 35 patients with new Q waves, 30 were men and 5 were women. The ages ranged from 36 to 67 years. Patients who had saphenous vein bypasses to all coronary arteries with luminal narrowing greater than 50% were considered complete revascularizations. Patients in whom saphenous vein bypass could not be performed to one or more vessels with luminal narrowing of greater than 50% were considered incomplete revascularizations.

RESULTS 1. Effects of Surgical Venting Technique Of 321 patients operated on, 104 (Group A, Table 1) had in tr a oper a t i ve v e n t r i c u l a r venting, while 217 (Group B, Table 2) had atrial v e n t in g during surgery. The incidence of new Q waves in Group A was 23/104 (22%) and in Group B, 12/217 (5.5%).

tients, 35 (11%) had new p o s t o p e r a t i v e Q waves. Of these, 8 (6.3%) occurred after single bypass in 127 patients, 20 (14%) after double bypass in 142 patients, and 7 (13.5%) after triple bypass in 52 patients. Complete revascularization was performed in 50/104 (48%) of p a t i e n t s with v e n t r i c u l a r vent i ng and 142/217 (65%) of patients with atrial venting. P a t i e n t s with new Q waves in group A had 13/23 (57%) com pl et e revasc u l a r i z a t i o n and in those of group B 6/12 (50%).

3. Relation of New Q Waves to Ungrafted Vessels or to Patent Grafts with Occluded Distal Artery New Q waves appeared in the zone of myocardium supplied by grafted arteries in all patients except two with v e n t r i c u l a r v e n t i n g (Case No. 6,7) in whom Q waves occurred within the zone of m y o c a r d i u m supplied by diseased, u n g r a f t e d vessels. Of all t h e patients with new Q waves who were restudied, only one, (Case 27), with atrial vent i ng and d e t e r i o r a t e d left v e n t r i c u l o g r a m , d e m o n strated p a t e n t grafts and an occluded coronary a r t e r y beyond the distal anastomotic site of t he graft.

2. Relation of New Q Waves to Number of Grafts Placed

4. Relation of New Q Waves to Postoperative Alteration of Left Ventricular Function and Graft Closure

In th e e n t i r e series of 321 o p e r a t e d pa-

In t h e 23 v e n t r i c u l a r v e n t e d p a t i e n t s TABLE I

Correlation of Number of Grafts, Patency Rate and New Q Waves in Patientswith Left Ventricular Venting Number

Post-Op Study

Grafts Closed

New Q Waves

No.

%

No.

No.

%

No.

%

23

22

3

3

%

Died

Patients

104

86

83

Grafts

157

122

78

27

22

LAD

82

67

82

6

9

RCA

50

40

80

15

38

CX

25

17

68

2

12

Single

51

40

78

15

38

6

1

Double

49

37

76

11G*

15

15

2

4

2

50

RCAt

17

2

0

Triple Abbreviations: LAD RCA CX tRCA "11G

= = = = =

Left anterior descending coronary artery Right coronary artery Circumflex coronary artery Only RCAgraft closure 11closed grafts in 8 patients (3 double and S single) J. ELECTROCARDIOLOGY, VOL. 9, NO. 4, 1976

NEW Q WAVES AFTER BYPASS GRAFTING

323

TABLE 2 Correlation of Number of Grafts, Patency Rate and New Q Waves in Patients with Left Atrial Venting Number

Post-Op Study

Grafts Closed

New Q Waves

No.

%

No.

No.

%

12

Patients

217

147

68

Grafts

406

265

65

18

7

LAD

192

134

70

7

5

RCA

117

78

67

6

8

CX

89

53

60

5

9

Single

76

60

79

4

7

Double

93

56

60

Triple

48

31

65

Died

%

No.

%

5.5

1

0.5

11G* 10 4Gt

4

Abbreviations: "11G = 11 closed grafts in 10 patients (1 double and 9 single) t 4G = 4 closed grafts in 4 patients ].

r[

TTT

OVR

QVL

OVF"

VI

V2

V3

V4

V5

V6

Fig. 1. Case 18 of Table 4. Serial EKGs, demonstrating inverted T waves in the anterior wall leads in the preoperative tracing (top) and less of R wave in leads V1-V2 in the two postoperative tracings. All saphenous vein bypass grafts were patent in this patient and postoperative left ventriculogram demonstrated improvement of left ventricular motion. (Group A) with new Q waves, 17 were studied postoperatively (Table 3). Five had single and 11 had double bypass grafts, while one had a triple bypass (an average of 1.8 grafts per patient). Of the 12 atrial vented patients (Group B) with new Q waves, 11 were restudied (Table 4), representing one single graft, 5 double and 5 triple grafts (an average of 2.4 grafts per patient), J. ELECTROCARDIOLOGY, VOL. 9, NO. 4, 1976

In Group A (ventricular venting), 17 patients with new Q waves had postoperative ventriculograms. Of these (Table 3), 3 (18%) had an improved v e n t r i c u l o g r a m a n d 0/7 graft closures, 4 (24%) had no change in the ventriculogram with 1/7 graft closure, and in 10 patients with deteriorated postoperative ventriculograms there were 7/16 graft closures (Table 4).

324

A I N T A B L I A N ET AL

TABLE 3 Correlation of Location of New O Wave, Patency of Graft, and Postoperative Ventriculogram in Group A Patients

Patient

Grafts LAD RCA CX

Patency LAD RCA CX

Contraction Preop Postop

HX MI

Admission EKG O Wave

New O

LVG improved

1.

X

X

+

+

As-Ant

Normal

+1

Inferior

Anterior

2.

X

X

+

+

As-Ant

Normal

+1

RBBB + Lateral

Inferior

3.

X

X

X

+

+

+

As-Ant

Normal

+1

Inferior (narrow Q)

Inferior (wide Q)

X

+

0

Normal

Normal

0

Normal

Septal

Normal

Normal

0

Inferior + Lateral

LAH + Anterior

LVG Unchanged 4. X

+

5.

X

6.

X

X

+

+

Normal Normal

0

Normal

Inferior

7.

X

X

+

+

Normal

Normal

+1

T11,111,AVF

Inferior

Ak-Apie Ak -Ant -Apic Normal AkApic

+3 0

TV1 _v 6

Anterior

Normal

Anterior

As-Apic AkApi . -Ant c Normal Ak-Apic

0 +2

Inferior

Anterior

T V1-V6

Anterior

As-Ant

Ak-Ant

0

LAH QRSWNL

Anterior

LVG Deteriorated 8. X

+

+

9.

X

0

10.

X

0

0

11.

X

0

O

12.

X

0

13.

X

X

+

+

Ak Ant

As-Ant Ak-lnf +Apic

+3

Anterior

Inferior

14.

X

X

+

+

As-lnf

Ak-lnf

0

Normal

Inferior

-t-

Normal Ak-Apic

0

Normal

Inferior

Normal Ak-Apic

0

IX]ormal

Lateral

Normal

I nferolateral

15.

X

16.

X

17.

X

0 X

+

+

In Group B (atrial venting), 11 patients with new Q waves were studied post-operatively. Of these, two had an improved ventriculogram and 0/6 graft closures. Six had an unchanged postoperative ventriculogram and 1/15 graft closures. Two had a deteriorated postoperative ventriculogram with 1/5 graft closures.

DISCUSSION Ventricular and Atrial Venting A striking decrease in the incidence of postoperative Q waves (from 22% to 5.5%) occurred when atrial rather than ventricular venting was adopted. The clear implication is

As-lnf

Ak -Inf -Apic

+2

t h a t sufficient myocardial t r a u m a r e s u l t s from ventricular vents to result in pathologic Q waves. The anatomic placement of ventricular vents at or near the apex corresponds with either inferior or anterior wall localization of the post-operative Q wave. Since the ventricular t r a u m a produced by venting is not due to arterial occlusion, there is no wide surrounding ischemic area. Thus, it is not surprising that postoperative Q waves attributable to venting are not always associated with impaired ventricular function in the absence of graft occlusion. Indeed, improved ventricular function m a y be observed. However, in four cases (13, 14, 15, 17) in which new inferior Q waves developed, new dysfuncJ. ELECTROCARDIOLOGY, VOL. 9, NO. 4, 1976

NEW Q WAVES AFTER BYPASS GRAFTING

13

I

Frl

aVL

aVR

aVF

Vl

V2

325

V3

V.

VS

Ve

Pre-op

~ post-op~

2 days post-op

20 days

Fig. 2. Case 26. Serial EKGs, demonstrating inverted T waves in Leads V1-V6 in the preoperative tracing (top) and appearance of Q waves in leads II, III and AVF in the postoperative tracings. Although the saphenous vein bypass graft was closed, postoperative left ventriculogram did not show deterioration.

TABLE 4 Correlation of Location of New Q Wave, Patency of Graft, and Postoperative Ventriculogram in Group B Patients

Patient

Grafts LAD RCA CX

Patency LAD RCA CX

Contraction Preop Postop

HX MI

Admission EKG Q Wave

New Q

LVG Improved 18. X

X

X

-I-

+

+

_~S_Apic-AntNormal

0

TV3-V 6

Septal

19.

X

X

+

+

-t-

As-Ant -Inf

Normal

0

Normal

inferior

X

-t-

+

Ak-lnf

Ak-lnf

+1

Inferior

Anterior

X

LVG Unchanged 20. X 21.

X

X

+

+

Normal

Normal

0

Normal

Inferior

22.

X

X

+

+

Normal

Normal

+1

TV3-V6

Inferior

23.

X

X

+

-t-

Normal

Normal

0

T 11,111. AVF

I nferior

24.

X

X

+

+

Normal

Normal

0

Normal

Inferior

25.

X

X

+

-t-

Normal

Normal

0

Normal

Inferior

Ak-lnf

Ak-lnf

0

TVI-V 6

Inferior

+

Normal

Ak -Ant -Apic

0

Normal

Anterior*

-t-

, -Ant ~S-Apic A k - A p i c

0

TV3-V 6

Lateral

26.

X

X

X

+

0

LVG Deteriorated 27. X X

X

+

28.

X

0

X

-t-

+

Abbreviations: LAD = Left anterior descending coronary artery RCA = Right coronary artery CX = Circumflex coronary artery HX MI = History of myocardial infarction LVG = Left ventriculogram As = Segmented hypokinesia Ak = Akinesia * Patent graft, but occluded distal left anterior descending artery J. ELECTROCARDIOLOGY, VOL. 9, NO. 4, 1976

326

AINTABLIAN ET AL

I

1-[

13[

aVR

aVE aVF

v2

v3

v4

vs

v6

Pre-op

2 days post-op

Fig. 3. Case 27. Serial EKGs, demonstrating normal preoperative EKG (top) and appearance of Q waves in the anterior wall leads in the three postoperative tracings. Although all grafts were patent in this patient, the distal left anterior descending artery was occluded beyond the anastomotic site and postoperative left ventriculogram showed deterioration. tion of the inferior wall and open grafts to the right coronary artery could be demonstrated. Here we assume t h a t the deterioration in the ventriculogram was probably secondary to the t r a u m a of venting. In contrast are six cases (9, 10, 11, 12, 16 and 28) all of whom developed new anterior Q waves and anterior wall dysfunction in the presence of occluded grafts to the left anterior descending artery. Here the presumption m u s t be t h a t infarction secondary to inadequate arterial and graft inflow occurred.

New Q Waves, Number of Grafts and Complete or Incomplete Revascularization The incidence of new Q waves was higher in p a t i e n t s with double and triple bypass surgery as compared to those with a single bypass, results similar to those reported by others. 4 However, in our series the incidence of new Q waves was not higher in patients with triple, as compared to those with double, vein bypass surgery, in contrast to the report of Espinoza and associates. 4 A l t h o u g h our p a t i e n t s with a t r i a l v e n t i n g had a h i g h e r p e r c e n t a g e of complete r e v a s c u l a r i z a t i o n , the incidence of new Q waves was not affected by complete or incomplete revascularization in patients within the atrial or ventricular venting group. It is worth mentioning t h a t in one p a t i e n t w i t h a t r i a l venting, a l t h o u g h saphenous vein bypass graft was patent, the coronary artery distal to the anastomosis was

closed, which explains the apearance of a new Q wave, as well as deterioration of left ventricular contractility.

Ventricular Function and Graft Patency Although Anderson and associates 8 noted no direct correlation between EKG evidence of t r a n s m u r a l myocardial infarction and graft closure, they did not comment on the ventriculographic findings. Brewer and associates 13 confirmed these findings in autopsy s t u d i e s of p a t i e n t s d y i n g a f t e r c o r o n a r y bypass surgery. In the present study, new Q waves were n o t e d in p a t i e n t s w i t h d e t e r i o r a t e d , unchanged, or even improved ventriculograms. When the data on new Q waves and posto p e r a t i v e v e n t r i c u l a r f u n c t i o n w e r e correlated, no direct relationship could be seen. However, when graft patency was also considered, a clear relationship emerged. Improved postoperative v e n t r i c u l a r f u n c t i o n correlated well with graft patency, despite Q waves. An unimproved or deteriorated ventricular function did not correlate with graft occlusion, since more t h a n h a l f of the vein grafts placed in these patients were patent. Assad-Morell and associates 14 also noted no correlation between graft closure, electrocardiographic and angiographic evidence of myocardial infarction because h a l f of their 32 patients had patent grafts, despite evidence of myocardial infarction in the area of distribuJ. ELECTROCARDIOLOGY, VOL. 9, NO. 4, 1976

NEW Q WAVES AFTER BYPASS GRAFTING

tion of the grafted vessels. It is important to note t h a t in our series, patients with single bypass grafts in whom the postoperative left ventriculogram showed deterioration invariably had occluded bypass grafts or a patent graft with occlusion of coronary artery distal to the anastomosis (Tables 3 and 4). Although one of our patients (Case 3), with history of previous myocardial infarction and narrow Q waves in the the inferior wall leads, posto p e r a t i v e l y developed s i g n i f i c a n t n e w Q waves in the same location and left ventricu l o g r a m showed i m p r o v e m e n t of a n t e r i o r wall motion with no change in the inferior wall motion, none of our patients after coron a r y bypass surgery manifested the phenome n o n of " u n m a s k i n g of old i n f a r c t i o n " described by Bassan and associates2

Q Waves and Atrial Venting When new Q waves appeared after bypass graft using the atrial venting technique, and v e n t r i c u l a r f u n c t i o n was u n i m p r o v e d or worsened, graft closure or occlusion of the distal coronary a r t e r y was common. Compromised arterial inflow and myocardial infarction must be presumed. Of great interest are those patients with new Q waves following atrial venting whose ventriculograms improved and whose grafts were patent. The new Q waves must be a consequency of surgical trauma. Two possibilities are suggested. First, direct myocardial damage with muscle necrosis m a y occur, sufficient to produce Q waves, but undetectable by v e n t r i c u l o g r a p h y . Second, the surgical t r a u m a might result in localized ventricular conduction d e l a y s or blocks affecting the early QRS balance, as postulated by Castellanos. 15 He theorized t h a t such local delays in ischemic tissue result in slurring or widening of the QRS, producing "infarct" Qs. It seems reasonable t h a t a similar mechanism in traumatized tissue may account for postoperative Q waves in these patients with improved ventriculograms and patent grafts.

Clinical Significance and Prognosis Post-bypass grafting Q waves, as described and discussed, have a varied pathogenesis. When accompanied by improvement in ventricular function and patent grafts, they are of little significance and do not carry the prognostic importance of myocardial infarction as it occurs in the n a t u r a l course of arteriosclerotic heart disease. In contrast, when accompanied by graft closure and deteriorated ventricular function, the mechanism may be presumed ischemic and the prognosis must take into account the likelihood of p e r m a n e n t or l o n g - t e r m localized ventricular dysfunction.

J. ELECTROCARDIOLOGY, VOL. 9, NO. 4, 1976

327

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