The effect of acute hypoxemia on coronary arterial dimensions in patients with coronary artery disease.

OBJECTIVES: To assess the influence of acute hypoxemia on the dimensions of diseased and nondiseased coronary arterial segments in humans. METHODS: In 18 subjects (age 53 +/- 8 years) with known or suspected coronary artery disease, quantitative coronary angiography was performed before and after being randomly assigned to breathing (1) an inspired oxygen concentration (fraction of inspired oxygen, FIO2) of 21% (room air, RA) for 20 min (n = 4, controls) or (2) an FIO2 of 15 and 10% for 10 min each (corresponding to altitudes of 2,500 and 5,500 m, respectively; n = 14). RESULTS: In the control subjects, no hemodynamic, oximetric or angiographic variable changed. In the 14 study subjects, the arterial partial pressure of oxygen averaged 85 +/- 13 mm Hg on RA, 65 +/- 15 mm Hg on 15% FIO2 and 44 +/- 13 mm Hg on 10% FIO2. Average arterial segment diameter was 2.52 +/- 0.63 mm on RA, 2.55 +/- 0.62 mm on 15% FIO2 (not significant vs. RA) and 2.66 +/- 0.66 mm on 10% FIO2 (p < 0.001 vs. RA). The increase in coronary arterial diameter with 10% FIO2 occurred only in normal segments (2.74 +/- 0.64 vs. 2.97 +/- 0.64 mm; p < 0.001), but not in diseased segments (2.34 +/- 0.57 vs. 2.38 +/- 0.55 mm; not significant). CONCLUSIONS: In humans, severe hypoxemia induces vasodilation of angiographically normal coronary arterial segments, whereas it causes no change in diseased segments.

Inaccuracies of oximetry in identifying the location of intracardiac left-to-right shunts in adults.

Although oximetric analysis of blood from the right heart chambers is the most commonly used method for assessing the presence of intracardiac left-to-right shunting, it sometimes provides misleading information because a patient with a left-to-right shunt in only 1 location sometimes manifests a significant oxygen step-up (1) in >1 chamber or (2) in a chamber other than that in which the shunt is actually located. This study was performed (1) to assess the frequency with which oximetric data provide such misleading results and (2) to determine which variables (if any) may contribute to the occurrence of such erroneous oximetric results. Accordingly, we analyzed oximetric data from 168 patients (61 men, 107 women, 14 to 76 years of age) with a proved left-to-right shunt at only 1 site and oximetric evidence of significant oxygen step-up. Using the criteria of Dexter et al (J Clin Invest 1947;26:554-560), Antman et al (Am J Cardiol 1980;46:265-271), or Pirwitz et al (Am Heart J 1997;133:413-417) for a significant oxygen step-up, 34%, 42%, and 35% of subjects, respectively, manifested a significant step-up in >1 chamber or a step-up only in an incorrect chamber. Compared with those with a step-up in the correct chamber only, those with a step-up in >1 chamber had larger Qp/Qs ratios (mean +/- SD, 2.7 +/- 1.2 vs 3.5 +/- 1.8, respectively, p <0.001), whereas subjects with a step-up only in an incorrect chamber had smaller Qp/Qs ratios than those with a step-up in the correct chamber (2.2 +/- 0.9 vs 2.8 +/- 1.3, respectively, p <0.001). In conclusion, in adult subjects with left-to-right intracardiac shunting in only 1 location, carefully obtained oximetric data often provide erroneous information.

Intra-aortic balloon counterpulsation.

Intra-aortic balloon counterpulsation (IABP) is sometimes used in critically ill patients with cardiac disease. By increasing diastolic arterial pressure and decreasing systolic pressure, it reduces left ventricular afterload. IABP may be beneficial in subjects with cardiogenic shock, mechanical complications of myocardial infarction, intractable ventricular arrhythmias, or advanced heart failure or those who undergo "high-risk" surgical or percutaneous revascularization, but the evidence to support its use in these patient groups is largely observational. Contraindications to IABP include severe peripheral vascular disease as well as aortic regurgitation, dissection, or aneurysm. The potential benefits of IABP must be weighed against its possible complications (bleeding, systemic thromboembolism, limb ischemia, and, rarely, death).

Predictors of coronary artery disease in patients with left bundle branch block undergoing coronary angiography.

Patients with left bundle branch block (LBBB) and concomitant coronary artery disease (CAD) have a worse prognosis than those with LBBB without CAD. In addition, subjects with CAD and concomitant LBBB have a higher cardiovascular mortality than those with a similar extent of CAD but without LBBB. Because the presence of LBBB makes the noninvasive identification of CAD problematic, patients with LBBB often are referred for coronary angiography to assess the presence and severity of CAD. To determine the clinical and demographic variables that might help identify those with CAD, we analyzed data from 336 consecutive patients with LBBB referred for coronary angiography. Of the 336, 54% had CAD. In conclusion, those with CAD were likely to be older, Caucasian, and men; they were more likely to have angina pectoris, myocardial infarction, and diabetes mellitus; and they were more likely to have a left ventricular ejection fraction <0.50. In contrast, patients with heart failure were less likely to have CAD.

Infarct-related coronary artery patency and medication use prior to ST-segment elevation myocardial infarction.

In patients who have ST-segment elevation myocardial infarction (STEMI), a patent infarct-related artery on the initial angiogram is associated with improved clinical outcomes, including decreased mortality. The present study assessed the influence of administering aspirin, beta blockers, statins, and angiotensin-converting enzyme inhibitors before STEMI on infarct-related artery patency. Our data demonstrate that patients who have STEMI and receive these medications on an outpatient basis before the event have a higher likelihood of having a patent infarct-related artery compared with patients who do not receive these medications. Further, our data demonstrate a graded association according to the number of such medications being administered: the likelihood of a patent infarct-related artery increased to >50% as the number of these medications increased.

Percutaneous coronary interventions: guidelines, short- and long-term results, and comparison with coronary artery bypass grafting.

An ever-growing number of patients are being referred for coronary revascularization in an attempt to reduce morbidity or to reduce mortality. Multiple randomized trials comparing percutaneous and surgical coronary revascularization have been performed. The decision to proceed with percutaneous or surgical revascularization should be based ona thorough understanding of the short- and long-term risks and benefits of each procedure in conjunction with the individual patient's coronary arterial anatomy and clinical risk profile.

Cardiac events in patients undergoing noncardiac surgery: shifting the paradigm from noninvasive risk stratification to therapy.

Internists and cardiologists are often asked to estimate the risk for perioperative myocardial infarction or cardiac death in patients being considered for noncardiac surgery. Estimating this risk in an individual patient is difficult and complex. Although noninvasive imaging tests are often used for this purpose, a review of the literature reveals that the positive predictive value of noninvasive imaging tests is uniformly low and that they do not provide information beyond that obtained by assessing simple clinical risk variables. Moreover, no evidence exists that noninvasive imaging tests lead to a therapeutic strategy that reduces the risk for perioperative myocardial infarction or cardiac death. Since the publication of guidelines for preoperative risk stratification by the American College of Cardiology/American Heart Association in 1996 and the American College of Physicians in 1997, three clinical trials have shown that beta-blocker therapy reduces the risk for perioperative cardiac events. This paper focuses on the relationship between risk stratification and subsequent therapy to minimize or eliminate risk. In short, the paradigm is shifting from predicting which patient is at high risk for having a perioperative cardiac event to minimizing the likelihood of such an event with specific perioperative pharmacologic therapy.

Reactivation of cardiac Chagas' disease in acquired immune deficiency syndrome.

We report the case of a 29-year-old man who developed acute congestive heart failure secondary to cardiac Chagas' disease in the setting of Trypanosoma cruzi reactivation by acquired immune deficiency syndrome.