Variability of myocardium at risk for acute myocardial infarction

Comparison of short-term clinical outcomes of proximal versus nonproximal lesion location in patients treated with primary percutaneous coronary intervention for ST-elevation myocardial infarction: The PROXIMITI study

OBJECTIVES

The objective of this study was to investigate the association of proximal and nonproximal location of culprit coronary lesions with clinical outcomes of patients presenting with ST-elevation myocardial infarction (STEMI) treated by primary percutaneous coronary intervention (PCI).

BACKGROUND

Proximal culprit lesion location in patients presenting with STEMI is associated with increased mortality when compared to distal culprit lesions in the thrombolytic era. The impact of lesion location on clinical outcomes in the era of PCI remains unclear.

METHODS

We analyzed 3,283 patients with STEMI who enrolled in the Victorian Cardiac Outcomes Registry. We compared outcomes in those with proximal lesion location versus patients with nonproximal location.

RESULTS

Of 3,283 participants, 1,376 (41.9%) had a proximal lesion location. Patients with proximal lesion location presented with greater rates of cardiogenic shock and out-of-hospital cardiac arrest, and left ventricular systolic dysfunction, all P < .01. Procedural success rates were similar (96% vs. 95%, P = .08). Patients with proximal lesion location had higher rates of in-hospital and 30-day mortality, major adverse cardiac events (MACE; mortality, myocardial infarction, stent thrombosis, and unplanned revascularization) and major adverse cardiac and cerebrovascular events (MACCE; MACE, and stroke) compared to the nonproximal group, all P < .001. However, on multivariable regression analysis, proximal lesion location was not independently associated with MACE during in-hospital stay or at 30-days (OR 1.32, 95% CI 0.95-1.83, P = .09 and OR 1.23, 95% CI 0.92-1.65, P = .15) respectively.

CONCLUSIONS

Patients with proximal lesion location had greater hemodynamic instability and higher-risk features; however, proximal lesions per se were not independently associated with worse clinical outcomes compared to nonproximal lesions.

Does Proximal Location of Culprit Lesion Confer Worse Prognosis in Patients Undergoing Primary Percutaneous Coronary Intervention for ST Elevation Myocardial Infarction?

ST segment elevation myocardial infarction (STEMI) from proximally located culprit lesion is associated with greater myocardium at jeopardy. In STEMI patients treated with thrombolytics, proximal culprit lesions are known to have worse prognosis. This relation has not been studied in patients undergoing primary percutaneous coronary intervention (PCI). In 3,535 STEMI patients with native coronary artery occlusion pooled from the primary angioplasty in myocardial infarction database, we compared in-hospital and 1-year outcomes between those with proximal (n = 1,606) versus non-proximal (n = 1,929) culprit lesions. Patients with proximal culprits were more likely to die and suffer major adverse cardiovascular events (MACE) during the index hospital stay (3.8% vs 2.2%, P = 0.006; 8.2% vs 5.8%, P = 0.0066, respectively) as well as during 1-year follow-up (6.9% vs 4.5%, P = 0.0013; 22% vs 17%, P = 0.003, respectively) compared to those with non-proximal culprits. After adjustment for baseline differences, proximal culprit was independently predictive of in-hospital death (adjusted odds ratio% 1.58, 95% confidence intervals, CI 1.05-2.40) and MACE (OR 1.41, CI 1.06-1.86), but not 1-year death or MACE. In addition, proximal culprit was independently associated with higher incidence of ventricular arrhythmias and sustained hypotension during the index hospitalization. The univariate impact of proximal culprit lesion on in-hospital death and MACE was comparable to other adverse angiographic characteristics, such as multivessel disease and poor initial thrombolysis in myocardial infarction flow, and greater than that of anterior wall STEMI. In conclusion, proximal location of the culprit lesion is a strong independent predictor of worse in-hospital outcomes in patients with STEMI undergoing primary PCI.

Quantification of myocardial hypoperfusion with 99m Tc-sestamibi in patients undergoing prolonged coronary artery balloon occlusion

Percutaneous transluminal coronary angioplasty provides an excellent opportunity to investigate the location and quantity of hypoperfusion during sudden complete occlusion of one of the major coronary arteries. Thirty-five patients referred for elective percutaneous transluminal coronary angioplasty were injected intravenously with 99mTc-sestamibi during balloon inflation. To visualize and quantify the hypoperfused region, a map of perfusion was constructed from that occlusion study and from the control study performed on the following day. Patients were divided into groups according to proximal or distal occlusion within each of the three coronary arteries. The region of myocardium supplied by each coronary artery varied in location and extended outside the typical borders for all arteries, but most prominently for the left circumflex coronary artery. The quantities of hypoperfusion varied within each artery group, but the average hypoperfusion was greater for the left anterior descending coronary artery than for either the right coronary artery or the left circumflex coronary artery. It is concluded that the quantities of hypoperfusion were highly variable within each artery group. Occlusion of the left anterior descending coronary artery was associated with the largest ischaemic region. The area of hypoperfusion extended outside the typical borders, most prominently for the left circumflex coronary artery.

A nonischemic electrocardiogram does not always predict a small myocardial infarction: results with acute myocardial perfusion imaging

BACKGROUND

A nonischemic electrocardiogram (ECG) in association with myocardial infarction (MI) indicates a small MI in some but not all cases. Myocardial perfusion imaging using technetium-99m sestamibi offers the ability to better characterize these "electrically silent" infarctions.

METHODS

Patients considered low risk for myocardial infarction with a normal or nonischemic ECG (no significant ST elevation, ST depression, ischemic T-wave inversion, or left bundle branch block) underwent early emergency department perfusion imaging, followed by serial myocardial marker sampling. Risk area (defect size) was quantitated by use of a 50% threshold from multiple short-axis slices.

RESULTS

A total of 87 patients with nonischemic ECGs had myocardial infarction (mean peak creatine kinase [CK] 710 +/- 720 U/L, range 111-3196 U/L). Peak CKs were lower in the 7 patients with negative perfusion imaging (420 +/- 290 U/L vs 730 +/- 740 U/L, P =.06). Mean risk area was 18% +/- 11% of the left ventricle (range 0%-62%) and was not significantly different among the different infarct-related arteries. Patients with normal ECGs had a similar risk area compared with other patients (16% +/- 12% vs 19 +/- 12%, P =.25). Coronary angiography was performed in 81 patients, with significant stenoses in 74 (91%) (37 one-vessel, 19 two-vessel, 18 three-vessel), with the infarct related artery most commonly the left circumflex (n = 32 [38%]).

CONCLUSIONS

The ischemic risk area in patients with a nonischemic ECG was comparable to patients with inferior ST-elevation myocardial infarction found in previous studies. A nonischemic ECG does not predict a small ischemic risk area.