Sane DC, Stump DC, Topol EJ, Sigmon KN, Clair WK, Kereiakes DJ, George BS, Stoddard MF, Bates ER, Stack RS, Califf RM.
Racial differences in responses to thrombolytic therapy with recombinant tissue-type plasminogen activator: increased fibrin(ogen)olysis in blacks. The Thrombolysis and Angioplasty in Myocardial Infarction Study Group.
Circulation 1991; 83(1):170-5.
(Comment in: Circulation. 1991;84(5):2205-7. Circulation. 1991;84(5):2205-7. )

The purpose of this study was to investigate outcome differences between black and white patients receiving thrombolytic therapy.

Data were derived from the TAMI-1 trial. Inclusion criteria for that study were persons who experienced acute myocardial infarction (AMI) for a specified duration and with specified clinical features. The exclusion criteria were recent trauma, major surgery internal bleeding, stroke; uncontrolled hypertension; prolonged cardiopulmonary resuscitation; serious advanced illnesses; age over 75 years; previous CABG surgery; and cardiogenic shock upon admittance.

All patients received an infusion of rt-PA in dosages that followed a specific protocol, and all patients received coronary arteriography and left ventriculagraphy. Other than patients with persistent occlusion or with more than 50% stenosis of the left main coronary artery, severe diffuse disease, cardiogenic shock, an unidentifiable infarct-related artery, or residual stenosis less than 50%, all patients were randomized to either receive either immediate or delayed (by one week) angioplasty. The report did not indicate the number of black and white patients receiving each type of treatment, nor whether patients were randomized to their treatment assignment or received treatments solely due to clinical characteristics.

The infarct patency rate significantly differed for blacks (91%) and for whites (72%). The authors state that "the higher patency rates in blacks suggest altered pharmacology of rt-PA or an increased sensitivity to fibrinolysis at equivalent re-PA levels." They conclude that "intrinsic differences may exist in the hepatic clearance of rt-PA between blacks and whites" but note that more detailed studies are necessary to evaluate this question.

Nadir fibrinogen levels were markedly lower for black patients than for white patients, and the change between baseline and nadir levels were greater. The authors state that this might be explained by the trend pattern of higher re-PT levels in blacks at the end of the maintenance period. Again, other factors should be investigated before drawing conclusions.

Rates of survival to discharge, 6- and 12-month survival, and CABG surgery were similar between blacks and whites. White patients were more likely to receive coronary angioplasty, especially during the acute period, but this was because the 90-minute patency rate was lower in white patients and the protocol mandated angioplasty of totally occluded vessels. There were no racial differences in occurrence of major overt clinical bleeding, but blacks received more transfusions. This excess occurred despite the fact that blacks underwent fewer angioplasty procedures during the acute period. In the follow-up, there was a trend toward more angioplasties being performed for blacks than whites, probably related to fewer having been done during the in-hospitalization period.

This study did not adjust for clinical or treatment differences and was limited to a very small number of black patients. Thus, it must be considered preliminary. The authors conclude that "the increased 90-minute patency rate after treatment of blacks with rt-PA may compensate for the reported worse prognosis of myocardial infarction in this population. This potential benefit should be weighed against the increased transfusion requirement. These findings raise the possibility that the rt-PA dosing regimen may need to be adjusted for blacks and other nonwhite races to achieve a maximal benefit to risk ratio."