Radionuclide assessment of cardiac function. Pre-operative evaluation of patients with abdominal aortic occlusive disease undergoing aortobifemoral bypass grafting

Routine Measurement of Radioisotope Left Ventricular Ejection Fraction Prior to Vascular Surgery: Is it Worthwhile?

OBJECTIVE

To determine whether estimation of left ventricular (LV) ejection fraction (EF) by means of multiple gated acquisition (MUGA) scanning could reliably stratify cardiac risk prior to elective major vascular surgery.

METHODS

A review of the English-language literature.

RESULTS AND CONCLUSIONS

Twenty-two studies enrolling a total of 3096 patients were identified from 1984 to date. Selection bias, blinding of the results, different cut-off limits, and several retrospective studies were some of the problems preventing a comprehensive analysis. The resting LVEF was not found to be a consistent predictor of perioperative ischaemic cardiac events. In the perioperative phase, poor LV function was, mainly, predictive of congestive heart failure, and, in the long-term, of cardiac outcome. The presence of myocardial wall motion abnormalities was also associated with both a higher chance of postoperative cardiac complications and a worse long-term cardiac outcome. Although measurements of LV function seem to play a key role in defining a patient's long-term prognosis, the value of routinely measuring LVEF preoperatively is limited and, therefore, MUGA scanning cannot be recommended as a general screening test. Despite this, it has been widely used for cardiac risk assessment in vascular surgery, and only recently its popularity has started declining. Other tests, such as stress-echocardiography and myocardial perfusion imaging, used selectively in moderate-risk patients can refine prediction of cardiac risk. In the future, gated stress myocardial perfusion scintigraphy, perhaps combined with ANP/BNP plasma level determination, may become a first choice test in preoperative cardiac risk assessment.

Very late survival after vascular surgery

PURPOSE

The aim of this study was to define very late survival in veterans who routinely underwent preoperative assessment of left ventricular function using radionuclide ventriculography (RNVG) before elective major vascular surgery from 7/84 to 7/88 at one Veterans Affairs Medical Center.

METHODS

RNVG defined left ventricular ejection fraction (EF) and determined the presence of ventricular wall motion abnormalities. Patients undergoing elective vascular surgery (n = 310) who had preoperative RNVG were then followed over the years using direct contact, VA administrative databases, and, most recently, the Social Security Death Index.

RESULTS

Follow-up was 6.64 +/- 4.62 years (range 0 to 16.2 years). Current survival is 10% (11/107) after carotid surgery, 12% (10/82) after aortic aneurysm repair, 15% (17/111) after extremity reconstruction, and 0% (0/10) after visceral artery reconstruction (ns). There was no statistically significant difference in mortality between the different types of vascular surgery at 30 days or at 1, 5, and 10 years after surgery (ns). Actual survival rates at 5 years after carotid surgery, aneurysm repair, extremity reconstruction, and visceral reconstruction were 55, 61, 59, and 50%, respectively. Stepwise logistic regression analysis was performed which included preoperatively defined cardiovascular risk factors, type of surgery, and results of RNVG. The final regression model indicated that age, diabetes, smoking at the time of surgery, and low EF were independently associated with overall mortality while angina, prior myocardial infarction (MI), and type of operation were not. Mean survival duration with normal EF (>50%) was 7.99 years versus 4.78 years with low EF (P < 0.001). No patient with severe left ventricular dysfunction (EF < or = 35%; n = 39) or who had postoperative cardiac complications (MI, CHF, ventricular arrhythmia; n = 38) survived to the present.

CONCLUSIONS

Very late survival after major vascular surgery was related to the presence of diabetes, active smoking at the time of surgery, left ventricular function, and postoperative cardiac complications. Since there was no association of overall mortality with angina or prior MI, an aggressive approach to coronary evaluation in such patients might not alter very late survival.

Radionuclide ventriculography and two dimensional echocardiography as predictors of left ventricular performance during aortic vascular surgery

Sixteen consecutive patients scheduled for elective aortic vascular surgery underwent preoperative LVEF determination employing two dimensional echocardiography (2DE) and radionuclide ventriculography (RNV). Measured and derived indices of cardiac function were recorded before and after induction of anaesthesia, aortic cross-clamping and aortic unclamping. Induction of anaesthesia was associated with significant decreases in mean arterial pressure (MAP), pulmonary capillary wedge pressure (PCWP), cardiac index (CI) and with a highly significant decrease in left ventricular stroke work index (LVSWI). Aortic cross-clamping was associated with significant increases in MAP and systemic vascular resistance (SVR) whereas aortic unclamping was associated with a significant decrease in SVR. Preoperative LVEF, as measured by RNV and 2DE, were similar. Resting ejection fractions correlated poorly with both preoperative cardiac indices and with changes in indices of left ventricular performance seen intraoperatively. Preoperative ejection fraction determination did not predict intraoperative left ventricular performance. Preoperative exercise scanning may prove more informative.

Assessment of myocardial function before aortic surgery by radionuclide angiocardiography

A consecutive series of 41 patients undergoing elective aortic surgery had pre-operative assessment of cardiac function by radionuclide angiocardiography. Their subsequent progress was monitored. There were 4 patients whose pre-operative left ventricular ejection fraction was less than 30 per cent and 3 of these patients died of cardiac failure postoperatively. There was only 1 death from cardiac failure amongst the 37 patients whose pre-operative left ventricular ejection fraction was less than 30 per cent. Radionuclide angiocardiography is an accurate indicator of myocardial function of patients before major aortic surgery.