Scand J Haemaiol - Suppl39, Vol30, 1983, 43-46

Fibrinolytic capacity after venous stasis in patients undergoing aorto-coronary by-pass surgery. Relation to shunt occlusion

HARALD ARNESEN, GUDMUND SEMB, RAGNAR HOL & HARALD KARLSEN

Medical Deparimeni 8, Deparimeni of Thoracic Surgery and Depariment of Radiology, Ullevd Hospital, Universiry Clinic, Oslo, Norway

In a prospective study 99 consecutive patients admitted for elective aorto-coronary by-pass surgery were subjected to estimation of their fibrinolytic capacity.

Reevaluation after 16 months included shunt angiography and repeated testing of the fibrinolytic capacity.

In the total material consisting of 244 grafts (2.7 per patient) 76 (31 To) were occluded. In the subgroup of 24 patients with reduced fibrinolytic capacity, 25 (38%) of the 66 grafts were occ- luded as compared to 53 (30%) of the 178 grafts in patients with normal fibrinolytic capacity (p = 0.2). The number of grafts per patient and the values of the peroperatively measured blood flow in the grafts were similar in the 2 groups.

Looking into the subgroup of grafts with “poor flow values” as measured peroperatively (=G 35 ml/min), 14 (78%) of 18 grafts were occluded in patients with reduced fibrinolytic capa- city, whereas 28 (53%) of 53 grafts were occluded in patients with normal fibrinolytic capacity (p = 0.06).

In conclusion, the present study is thought to indicate that reduced fibrinolytic capacity might be an additional risk factor for graft occlusion in patients undergoing aorto-coronary by-pass surgery, particularly so in grafts where low blood flow values are obtained.

Key words: Aorto-coronary by-pass - Fibrinolytic capacity - Graft patency

Aorto-coronary by-pass surgery is widely adopted in patients with severe angina pecto- ris. The success of the operation depends on the persisting graft patency, in addition to the completeness of revascularization and the progression of the atherosclerotic disease in the native coronary circulation (Robert et al. 1978, Hamby et al. 1979, Lawrie et a]. 1 980).

Graft patency has mainly been related to mechanical factors like the degree of coro- nary atherosclerosis, particulary the distal vessel run-off, the size of the grafted artery,

the size and type of by-pass, and to surgical technical factors as well (Bourassa et al. 1972, Balderman et al. 1980). These factors are more or less expressed in the peropera- tively measured blood flow of the by-pass, being the dominating singleDparameter in the prediction of graft patency. In addition, Zajtchuk et al. (1977) have pointed out the possible role of a hypercoagulable state.

Reduced fibrinolytic activity after venous occlusion is frequently observed in people with recurrent venous thromboembolism (Isacson & Nilsson 1972), and a disordered

44 H. ARNESEN, G. SEMB, R. HOL & H. KARLSEN

fibrinolytic potential has been described in patients with angiographic evidence of coro- nary heart diesease (Walker et al. 1977).

The present prospective study was under- taken to evaluate the possible importance of the fibrinolytic capacity as measured after venous occlusion, for the maintenance of graft patency in patients undergoing aorto- coronary by-pass surgery for severe angina pectoris.

PATIENTS AND METHODS Patients. The study comprises 99 patients consecutively admitted for elective aorto-coronary by-pass operation because of severe stable angina pectoris. At the follow- up examination after 16 months (mean, range 11-22 months) 5 patients were dead (between days 2 and 90 postoperatively) and 4 refused another angiography. Thus, the present follow-up study comprises 90 patients, 78 men and 12 women with a mean age at follow-up of 57 years (range 38-74).

The saphenous vein was used for by-pass in all patients, and the 90 patients received altogether 244 grafts, that is 2.7 per patient as a mean. This number of grafts per patient was similar in all groups of patients to be compared.

Methods Fibrinolytic capacity. On admittance for the elective aorto-coronary by-pass surgery all patients were subjec-

ted to analysis of theire fibrinolytic capacity after venous occlusion. Venous occlusion was performed ac- cording to Robertsson et al. (1972) with 90 mm Hg pres- sure in the sphygmomanometer cuff on the upper arm for 20 min.. Estimation of the fibrinolytic capacity of the individual was performed using the euglobulin clot lysis time as described by Nordby et al. (1980). With this method an arbitrary upper normal limit is set at 45 minutes.

In all patients with an abnormally low fibrinolytic capacity (31 out of 90) the test was repeated at the follow-up examination.

Blood flow measurements were performed in the grafts peroperatively by an electromagnetical method as de- scribed by Cappelen & Hall (1969).

Selective shunt angiography was performed at the follow-up examination in all patients using a standard- ized procedure with Judkins catheter. All patients were asked for their consent and 4 patients refused the re- peated arlgiography (vide supra). The angiograms were evaluated by our radiologist without knowledge of the fibrinolytic capacity and the flow values in the grafts of the individual.

N o complications to the shunt angiography were re- corded.

RESULTS

Reduced fibrinolytic capacity. The group of patients with reduced fibrinolytic capacity on both examinations (Cfr. Pat and meth)

TABLE 1

Fibrinolytic capacity as related to graft occlusion at follow-up

No of N o of Patent Occluded patients grafts grafts grafts

No Yo No %

Total material 90 244 166 68 78 32

Normal fibrinolytic capacity

66 178 125 70 53 30

Reduced fibrinolytic capacity

24 66 41 62 25 38;

* p = 0.2

FIBRINOLYTIC CAPACITY AND GRAFT PATENCY 45

consisted of 24 individuals (27%) receiving 66 grafts, leaving 66 patients with 178 grafts to the group with normal fibrinolytic capa- city. The 2 groups were comparable with re- gard to age, sex, number of grafts per patient and blood flow values in their grafts.

Peroperative blood flow values in the grafts. The mean blood flow in the total material of 244 grafts was 64 ml/min. with a range of 0-225 ml/min.. The mean blood flow in the 166 grafts which were found to be patent at follow-up was 74 ml/min. (range 10-225) as compared to 41 ml/min. (range 0-140) in the 78 grafts which were found occluded. This difference between the blood flow values in the 2 groups is statistically signifi- cant (p < 0.01).

Fibrinolytic capacity as related to graft oc- clusion. (Table I ) . Of the 178 grafts in the 66 patients with normal fibrinolytic capacity, 53 (30%) were found occluded at follow-up. In the 24 patients with reduced fibrinolytic capacity, 25 (38%) out of 66 grafts were found occluded. This difference may reflect a trend, but is statistically not significant (p = 0.2).

The subgroup of grafts with “poor flow values” as defined to be d 35 ml/min. con- sisted of 71 (29Vo), 42 of which were found occluded (59%) (Table 11). In this subgroup 53 grafts belonged to patients with a normal fibrinolytic capacity, and 28 (53%) were oc- cluded. In patients with reduced fibrinolytic capacity 14 (78%) out of 18 such grafts were occluded. This difference in occlusion rate between grafts with “poor flow values” in patients with normal or reduced fibrinolytic capacity is statistically significant (p = 0.06).

DISCUSSION

In the present study follow-up angiography of the grafts was performed after 16 months as a mean. The frequency of occluded grafts was high (32%) and obviously related to “mechanical factors’’ as reflected in the per- operatively measured blood flow values of the grafts. Thus, this blood flow values seems to be the most important single prognostic parameter for late patency of the grafts. The various determining factors behind this para- meter will, however, not be discussed in the present publication.

TABLE I1

Occlusion of grafrs with “poor blood flow” (< 35 ml/min) as related lo fibrinolytic capacity

No of Patent Occluded grafts grafts grafts

No vo N o 070

Total material 71 29 41 42 59

Normal fibrinolytic capacity

53 25 47 28 53

~

Reduced fibrinolytic capacity

18 4 22 14 78’

* p = 0.06

46 H. ARNESEN, G. SEMB, R. HOL & H. KARLSEN

Reduced fibrinolytic capacity was found in 27% of the patients on both examinations. This is close to the figures reported by Wal- ker et al. (1977) for “disordered fibrinolytic potential” in patients with angiographic evi- dence of coronary heart disease. In the pre- sent study, the groups of patients with nor- mal or reduced fibrinolytic capacity were al- most identical with regard to age, number of grafts per patient and blood flow values in the grafts. In the entire group a trend to- wards proneness for graft occlusion in pat- ients with reduced fibrinolytic capacity was recorded, although statistically not signifi- cant. This trend was, however, more pro- nounced in grafts with “poor flow values”.

Thus, in addition to the dominating “mechanical factors” as expressed in the blood flow values in the grafts, the individual capacity to dissolve initial thrombus forma- tion may be of importance for late graft pa- tency. It seems logic to assume that the pro- cesses of thrombus formation and dissolu- tion become relatively more important with decreased blood flow values. This may further be of future interest for the selection of patients for therapeutic stimulation of the fibrinolytic system or anticoagulation after aorto-coronary by-pass surgery.

REFERENCES

Robert EW, Guthaner DF, Wexler L & Alderman EL (1978) Six-year clinical and angiographic follow-up of patients with previously documented complete re- vascularization. Circulation 58 (suppl I ) , 1, 194-99.

Hamby R1, Aintablian A, Handler M, Voleti C , Weisz D, Garvey JW & Wisoff G (1979) Aortocoronary saphenous vein bypass grafts. Circulation 60, 901- 09.

Lawrie GM, Morris GC, Silvers A & Chapman D (1980) Residual lesions after coronary bypass: an important variable affecting late survival. Am J Cardiol45,418.

Bourassa MG, Lesperance J , Campeau L & Simard P (1972) Factors influencing patency of aortocoronary vein grafts. Circulation 45 (suppl 1) 1, 79-85.

Balderman SC, Moran JM, Scanlon PJ & Pifarre R (1980) Predictors of late aortocoronary graft patency. J . Thorac Cardiovasc Surg 79, 724-28.

Zajtchuk R, Collins G J , Holley PW, Heydorn WH, Schuchmann G F & Hamaker WR (1977) Coagulation factors influencing thrombosis of aorto-coronary by- pass grafts. J Thorac Cardiovasc Surg 73, 309-1 I .

lsacson S & Nilsson IM (1972) Defective fibrinolysis in blood and vein walls in recurrent “idiopathic” venous thrombosis. Acta Chir Scand 138, 313-19.

Walker ID, Davidson JF, Hutton 1 & Lawrie TDV (1977) Discordered “fibrionolytic potential” in coro- nary heart disease. Thromb Res 10, 509-20.

Robertsson BR, Pandolfi M & Nilsson 1M (1972) Re- sponse of local fibrinolytic activity to venous occlu- sion of arms and legs in healthy volunteers. Acta Chir Scand 138, 437-40.

Nordby E, Arnesen H , Andersen P & Godal H C (1980) The euglobulin clot lysis time, a rapid and sensitive method for the assay of fibrinolytic activity after venous stasis. Scand J Haemat 25, 407-11.

Cappelen C & Hall K V (1969) lntraoperative blood flow measurements with electromagnetic flowmeter. Progr. in Surg. 8, 102-23.