were 23 f 28 mg/dl (mean f standard deviation) in patients with restenosis, and 20 f 26 mg/dl in those without (p = not significant). Elevated LP(a) levels >20 mg/dl Qiu et al’ showedthat lipoprotein were found in 13 of 34 patients with (a) (LP[a]) levels are not increased restenosis and in 10 of 31 without. in unstable angina pectoris, myoAlthough LP(a) is a proven risk cardial infarction and after throm- factor for coronary heart disease bolytic therapy, although there is and reocclusion after coronary bysubstantial evidencethat LP(a) is a passsurgery, our observations indigenetically influenced independent cate that LP(a) serum concentrarisk factor for coronary heart dis- tion doesnot correlate with risk for ease.2*3LP(a) is present in athero- restenosis after PTCA. Martin Schumacher, MD sclerotic plaques and is deposited in Andreas liran, YID vein grafts after coronary bypass Bemd Eber, MD Hermann Toplak, MD surgery.4 Moreover, LP(a) concenMartie Wi~-Tm8Chttig, MD tration in serum is a predictor of Werner Klein, MD vein graft occlusion after bypass Graz, Austria 21 August 1991 surgery.5y6 Whether LP(a) is a prognostic factor for restenosis after percutaneous transluminal coronary angioplasty (PTCA), which 1. Qui S, ThCroux P, Genest J Jr, Solyrepresents the main problem limit- moss BC, Robitaille D, Marcil M. Lipoing the long-term efficacy of this protein (a) blood levels in unstable angina acute myocardial infarction, and procedure, is not yet known. The pectoris, after thrombolytic therapy. Am J Cardiol frequency of restenosis 3 to 4 1991;67:1175-1179. months after PTCA is approxi- 2. Seed M, Hoppichler F, Reaveley D, mately 25 to 35%.l Therefore, we McCarthy S, Thomson GR, Boerwinkle studied LP(a) serum concentra- E, Utermann G. Relation of serum lipotions in a series of 65 men (mean protein (a) concentration and apolipoproage 55 years, range 38 to 70) with tein (a) phenotype to coronary heart discoronary heart diseaseand success- ease in patients with familial hypercholesful PTCA. LP(a) was measured by terolemia. N Engl J Med 1990;322: 1494Laurel1 electrophoresis (ready-to- 1499. Dahlen GH, Guyton JR, Attar M, use agar gel, Immuno, Vienna, 3. Farmer JA, Kautz JA, Gotto AM. AssoAustria). Follow-up coronary angi- ciation of levels of lipoprotein Lp(a), plasography was performed 12 months ma lipids, and other lipoproteins with corafter PTCA. LP(a) values were de- onary artery disease documented by angitermined 12 months after this angi- ography. Circulation 1986;4:758-765. ography. Restenosiswas defined as 4. Rath M, Niendorf A, Rebin T, Dietel >25% decreaseof the initial result M, Krebber HJ, Beisiegel U. Detection and >50% stenosisof the vesseldi- and quantification of lipoprotein (a) in ameter. Thirty-four patients had the arterial wall of 107 coronary bypass restenosis (mean age f standard patients. Arteriosclerosis 1989;9:579592. deviation 56 f 8 years) and 31 did 5. Cushing GL, Gaubatz JW, Nava ML, not (55 f 9 years). Burdick BJ, Bocan TMA, Guyton JR, Both groups did not differ signifi- Weilbaecher D, DeBakey ME, Lawrie cantly in medical history (smoking GM, Morrisett JD. Quantitation and lohabits, hypertension and family his- calization of apolipoproteins (a) and B in tory), routine lipid profile (total coronary artery bypass vein grafts resectcholesterol, high- and low-density ed at re-operation. Arteriosclerosis 1989; lipoprotein cholesterols, triglycer- 9593-603. ides, and apolipoproteins Al and B) 6. Hoff HF, Beck GJ, Skibinski CJ, Jiiror fibrinogen levels. LP(a) values gens G, O’Neil J, Kramer J, Lytle BSS. Lipoprotein (a) is Not a Risk Factor for Restenosis After Percutaneous Transluminal Coronary Angioplasty

Letters (from the United States) concerning a particular article in the Journal must be received within 2 months of the article’s publication, and should be limited (with rare exceptions) to 2 double-spaced typewritten pages. Two copies must be submitted.

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Serum Lp (a) level as a predictor of vein graft stenosis after coronary artery bypass surgery in patients. Circulation 1988;6: 1238-1244.

7. Serruys PW, Luijten HE, Beatt KJ, Geuskens R, DeFeyter PJ, Brand M, Reiber JHC, Katen HJ, Es GA, Hugen-

THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 69

FEBRUARY 15. 1992

holtz PG. Incidence of restenosis after successful coronary angioplasty. Circulation 1988;77:361-371.

Thallium Stress Tests in Asymptomatic Diabetics

Langer et al’s’ May 15, 1991, article in the Journal adds to the growing number of reports on silent myocardial ischemia in adults with diabetes mellitus. I disagree with 1 of their conclusions. They state: “Although coronary angiography was not performed in our subjects, previous studies have shown that thallium scintigraphy identified 97% of asymptomatic subjects with abnormal electrocardiograms correctly regarding the presenceor absence of coronary artery disease.” They reference a study that looked at asymptomatic air crew members with computer-enhanced thallium201 scintigraphy.2 Those patients are not comparable to their subjects. The patients in Langer et al’s study had normal 1Zlead electrocardiograms. There is a big difference. One cannot assume that Langer et al’s subjects with abnormal thallium images had significant coronary artery disease. There are 7 other published studies describing asymptomatic adults with diabetes mellitus and the presence of myocardial ischemia.3-9 One study usedboth exercisethallium imaging and coronary arteriography.9 One hundred thirty-six asymptomatic adults with diabetes mellitus were screenedfor the presence of coronary artery disease. These patients had no clinical or electrocardiographic evidence of heart disease;39 had either an abnormal exercise electrocardiogram or postexertional thallium image, or both, and 33 underwent cardiac catheterization with coronary arteriography. Sixty percent of the patients with an abnormal postexertional thallium image had no significant coronary artery disease as defined by coronary arteriography. Noninvasive tests for detecting the presenceof coronary artery diseaseare not 100%specific. The relatively low prevalence of coronary artery diseasein asymptomatic patients results in low positive predic-