Reversal of Exertional Hypotension After Coronary Bypass Grafting

WEI-I LI, MD, FACC ROBERT C. K. RIGGINS, RICHARD P. ANDERSON, Seattle,

MD, FACC MD

Washington

A decrease in systolic blood pressure that occurs with treadmill exercise testing may be a sign of reversible ischemic left ventricular dysfunction. To test this hypothesis, we examined retrospectively the postoperative treadmill responses of 37 patients who had exertional hypotension (end exercise systolic blood pressure less than or equal to initial preexercise levels) before coronary arterial bypass grafting. This group of 37 patients was characterized preoperatively by an abnormal exercise electrocardiogram (36 patients), multiple vessel occlusive disease (36 patients) and a normal ejection fraction at rest (32 patients). Postoperative exercise tests showed improvement in hemodynamic and electrocardiographic changes with reversal of exertional hypotension (33 patients), and conversion to a normal exercise electrocardiogram (29 patients). Coronary bypass surgery can be expected to reverse exertional hypotension in patients with symptomatic angina pectoris and evidence of ischemia in the exercise electrocardiogram.

The normal hemodynamic response to upright treadmill exercise includes a sustained increase in systolic blood pressure.’ An abnormal decrease in systolic blood pressure occurs during treadmill exercise in a subgroup of patients with coronary atherosclerosis; this decrease may, in part, be caused by acute ischemic left ventricular dysfunction.2,” Coronary bypass surgery improves the functional status of patients with angina. This improvement has been corroborated by data obtained during objective testing with treadmill exercise,4,5 atria1 pacing6 and measurement of lactate extraction across the myocardium.7ss Revascularization of ischemic myocardium might also be expected to improve abnormal exercise hemodynamic responses. We tested this hypothesis by analyzing the postoperative treadmill test results in a subgroup of patients with symptomatic angina pectoris who demonstrated exertional hypotension before coronary bypass grafting. Methods

From the Sections of Cardiothoracic Surgery and Cardiology, The Mason Clinic, Seattle, Washington. Manuscript received February 27, 1979; revised manuscript received May 1, 1979, accepted May 2, 1979. Address for reprints: Wei-i Li, MD, Section of Cardiothoracic Surgery, The Mason Clinic, 1100 Ninth Avenue, Seattle, Washington 98101.

Patients: Thirty-seven patients who manifested exertional hypotension during preoperative treadmill exercise testing constituted the study group. There were 32 men and 5 women with a mean age of 55 years (range 40 to 70). These patients were retrospectively identified from a consecutive series of 360 patients undergoing isolated coronary arterial bypass surgery for symptomatic angina pectoris between October 1974 and January 1978 at this institution (1 patient in this group [0.28 percent] died within 30 days of operation). Preoperative treadmill exercise tests were performed in 234 patients of whom 55 (24 percent.) had exertional hypotension, defined as an end systolic blood pressure equal to or less than the preexercise standing level. Eighteen of the 55 patients were excluded from the study because they lacked a postoperative test or were receiving propranolol, antihypertensive drugs, digitalis or diuretic drugs at the time of preoperative testing.

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TABLE Summary

of 37 Cases Preoperative Data

Case no.

EF 0.70 0.81 0.62 0.39 0.83 0.58 0.60 0.80 0.70 0.82 0.40 0.82 0.81 0.82 0.68 0.67 0.47 0.69 0.45 0.21 0.73 0.72 0.67 0.72 0.74 0.57 0.72 0.63 0.33 0.74 0.69 0.91 0.57 0.52 0.60 0.63 0.86

l

CAD

SBP at Rest 130 155 124 142 165 144 150 152 178 165 130 148 132 160 134 130 148 130 130 116 120 180 118 138 100 170 156 110 140 140 154 152 148 124 140 160 146

HR at Rest

ASBP -50

-70 1:: 80

-58 -44 -45

::

-34 -40

z: 120 88

-48 -23 -10 -10

:: 100

-18 -2

;z

-z -14

;: 90

-20 -28 -20

72 ;: 75 76 74 73

-,:

:: 100 86 70

-14 -30 -20 -30 -54

z 55

-2 -4 -4

1:: 76

-38

-z 0 -10 -40

:

AHR

RPP

+29 +62 +65 +22 +45 +59 +62 +100 +65 +22 +57 +85 +22 +55 +140 +72 +67 +91 -l-43 +68 +54 $76 -l-57 +98 +70 +117 +104 +57 +50 +56 +75 -l-80 +61 +85 +30 +44 +54

128 184 109 150 160 141 225 218 220 194 268 156 248 151 197 182 189 151 154 145 295 110 237 144 247 227 98 180 156 145 222 230 168 140 236 140

94

Exercise Time (min) 2.8 3.2 1.6 3.3 4.0 5.0 5.3 2.8 2.8 7.2 4.8 7.7 3.5 3.0 3.7 7.6 2.1 3.4 2.7 2.8 4.8 7.0 3.1 6.6 6.9 6.5 8.3 4.6 6.3 5.1 6.7 2.0 5.2 6.3 3.0 4.7 4.4

FAI

Exercise ECG Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal

Left main coronary arterial stenosis. CAD = coronary artery disease (no. of vessels involved);EF = ejection fraction; FAI = functional aerobic impairment: HR = heart rate (beats/min);

Exercise testing: All patients in the study group performed exercise according to the Bruce multistage protocol.g Cuff blood pressures were measured at 1 minute intervals with a mercury-calibrated anaeroid sphygmomanometer. The highest systolic blood pressure and heart rate within each 3 minute interval and the final values at the end of exercise were recorded. A 12 lead electrocardiogram was continuously recorded during and for 9 minutes after exercise. The difference between the last systolic blood pressure recorded during exercise and the initial standing preexercise systolic blood pressure was calculated for each patient; ratepressure product and functional aerobic impairment were derived from exercise data as additional performance indexes. Postoperative testing was performed within 9 months (mean 3.7) after operation. The statistical significance of differences observed for each performance index was calculated by a paired t test. An abnormal exercise electrocardiographic response was defined as a flat or downsloping S-T segment depression equal to or greater than 1 mm and of 0.08 second duration in at least

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three consecutive complexes, occurring during or after exercise. When the resting electrocardiogram showed S-T depression, these criteria were doubled, with a 2 mm depression below baseline required to define an abnormal response. A borderline response was either a flat S-T segment of less than 1 mm depression or a junctional upward sloping S-T segment that remained 1 mm below baseline at 0.06 to 0.08 second after the ,J point in the postexercise tracing. Cardiac catheterization and operation: Selective coronary arteriograms were performed in multiple projections and recorded on 35 mm tine film. An occlusive lesion greater than 50 percent of vessel diameter was considered critical. A single plane left ventriculogram was obtained in the right anterior oblique projection before coronary angiography, and ejection fraction was calculated by the area-length method.lO Our previously described techniques l1 of coronary bypass grafting were employed with exclusive use of an autogenous saphenous vein. The average number of grafts placed per patient was 2.8. One patient received a single graft, 10 patients received two grafts, 23 received three grafts, two received four grafts, and one received five grafts.

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TABLE Summary

of 37 Cases Postoperative Data

Case no.

23 ;z 26

:3

34 35 36 37

SBP at Rest 128 138 130 130 180 128 144 142 120 156 142 130 128 160 138 114 148 128 152 128 110 164 104 140 120 130 130 120 148 138 144 152 144 130 124 146

HR

at Rest 78 100 9”: z: 92 101 75 112 110 1:: 99 :: 1:: 105 78 94 :: 94 1:: :: 104 90 :: 89 70 90 105 82

ASBP

AHR

RPP

+44 +18 +20 +30 +50 +28 +42 +68 +40 +74 +56 +50 +66 -l-70 +42 +42

+87 +65 +100 +90 +112 +90 +70 +68 +76 +79 +70 +109 +75 +81 +63 +94 +80 +69 -75 +102 +76 +112 +86 +91 +96 +72 +80 +66 +68 +80 +106 +67 +99 +83 +48 +45 +68

283 257 252 228 391 280 301 354 275 414 374 327 349 414 275 296 261 326 381 338 255 410 324 381 227 361 272 246 309 340 331 284 258 198 165 165 204

+‘6: +60 +60 +40 +50 +76 +66 +14 +60 +58 +34 +40 +62 +40 +28 +10 0 -6 -36 0

Exercise Time (min)

Exercise ECG

FAI

9.3

6.8 7.3 9.5 9.3 9.4 9.9 6.3 8.7 11.2 7.8 9.1 9.5 6.1 7.0 10.8 8.4 7.3 9.7 9.1 9.5 9.4 9.8 6.8 8.8 9.1 9.4 8.4 9.3 6.3 8.4 3.0 7.6 5.2 4.8 4.0 7.2

-1; 25 -12 -12 -,; -20 -z 7 1; -3 12 0 :: 0 -12 -2 0 -7 1; 7 -17 0 -3 0 -1 49 22 40 41 43 14

Normal Normal Normal Normal Normal Normal Normal Normal Normal Normal Normal Normal Normal Normal Normal Borderline Borderline Normal Normal Borderline Normal Normal Normal Normal Normal Normal Borderline Normal Normal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal Abnormal

AHR = end exercise heart rate - heart’rate’at’rest; RPP = rate-pressure product = systolic blood pressure X heart rate X lO-‘$ SBP = systolic blood pressure (mm Hg); ASBP = end exercise systolic blood pressure - resting systolic blood pressure.

One perioperative myocardial infarct occurred (3 percent). This was a nontransmural infarction occurring 4 days after double vein grafting (Table I, Patient 32).

Results The results of cardiac catheterization and treadmill exercise testing for all 37 patients are listed in Table I. Preoperative cardiac catheterization: Multiple vessel involvement was present in most of the 37 patients. Triple vessel disease was present in 27 patients (73 percent), double vessel disease in 9 patients (23 percent) and single vessel disease in only 1 patient. Critical left main coronary arterial stenosis was present in 13 patients (35 percent). With involvement of the left main coronary artery counted as double vessel disease, the average number of jeopardized major vessels per patient was 2.7. Five patients had impaired left ventricular systolic pump function with an ejection fraction

of less than 0.50 (Table I). The mean ejection fraction

was normal (0.65). Left ventricular end-diastolic pressure ranged from 2 to 26 mm Hg (mean 10) before ventriculography and from 5 to 36 mm Hg (mean 18) afterward. Stress tests: Table II lists the mean values, standard errors and statistical significance of the pre- and postoperative performance indexes listed in Table I. The mean change in the difference between the last and preexercise systolic blood pressure values (ASBP) before operation was -23 mm Hg and after operation was +40 mm Hg; the net postoperative increase in ASBP of 63 mm Hg was highly significant (Fig. 1). The observed changes in heart rate, rate-pressure product and functional aerobic impairment also showed significant increases. Whereas all patients had abnormal electrocardiographic exercise responses preoperatively, the postoperative tracings were normal in 25 patients, borderline

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fatigue, dyspnea and leg weakness in the remaining 31. Five of the six patients who had exertional angina postoperatively underwent repeat angiograpby (Table III). Occlusion of one graft, progressive disease in the native vessels or distal occlusive disease with patent grafts, alone or in combination, were found in these patients.

TABLE II Pre- and Postoperative Treadmill Exercise Performance Indexes in 37 Patients Performance

Preoperative

Index’

-23f3 +64&4 179 f 4.6 f

ASBP (mm Hg) AHR (beatsjmin) Bate-pressure product Duration of exercise (min) Functional aerobic imoairment t %) * Mean values f P = probability.

45 f

Postoperative +40 f +81 f 300f 8.1 f

8 0.3 7

5 3 11 0.3

4f3

P Value