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Quantification of myocardium at risk in unstable angina: comparison of patients with and without previous infarction
Insights
Patients with unstable angina and prior myocardial infarction have more severe coronary artery disease. However, the amount of heart muscle at risk of damage remains similar between groups.
Area of Science:
- Cardiology
- Cardiovascular Disease
- Myocardial Infarction
Background:
- Unstable angina pectoris (UAP) is a critical condition requiring risk stratification.
- Previous myocardial infarction (MI) may influence the severity of coronary artery disease (CAD) in UAP patients.
Purpose of the Study:
- To compare the extent and severity of CAD in UAP patients with and without a history of MI.
- To assess the amount of jeopardized myocardium in these patient subgroups.
Main Methods:
- Two patient groups were studied: 35 UAP patients without prior MI (Group A) and 73 with prior MI (Group B).
- Coronary artery disease severity was assessed using a scoring system quantifying percent myocardium threatened by stenosed arteries.
- Myocardial infarction extent was estimated using a wall motion score, and myocardium in jeopardy was calculated.
Main Results:
- Patients with prior MI exhibited significantly more severe and extensive CAD, including a higher number of stenotic arteries and greater percent myocardium threatened (68.7% vs. 53.6%, P<0.01).
- The proportion of infarcted myocardium was significantly higher in the prior MI group (24.2% vs. 1.6%, P<0.01).
- Despite differences in CAD severity and infarcted muscle, the percentage of myocardium still in jeopardy was not statistically different between groups (44.2% vs. 51.8%).
Conclusions:
- Patients with unstable angina pectoris and a history of myocardial infarction present with more severe coronary artery disease.
- The amount of left ventricular myocardium remaining in jeopardy is comparable between UAP patients with and without previous myocardial infarction.
Abstract:
We studied two subgroups of patients with unstable angina pectoris: 35 without (Group A) and 73 with (Group B) previous myocardial infarction. The severity of coronary artery disease was assessed by means of a previously described scoring system. This scoring system was used to calculate the proportion of left ventricular myocardium fed by significantly (greater than 75% luminal area reduction) stenosed coronary arteries (called percent myocardium threatened). To estimate the amount of myocardium lost by previous infarction we used a four-point wall motion score for each of seven left ventricular wall segments: a value of 2 was given to normokinetic segments, 1 for hypokinetic segments, 0 for akinetic and -1 for dyskinetic segments. The deficit in wall motion score was used to estimate the amount of myocardium infarcted. This was then subtracted from the proportion of myocardium threatened to yield the proportion of myocardium still in jeopardy. We found a different extent and severity of coronary artery disease between the two subgroups. In the group without previous infarction, the numbers of patients with one-, two- and three-vessel disease were 15, 9, and 11, respectively (or 43, 26, and 31%). In those with a previous infarction, the respective numbers were 11, 23, and 39 (or 15, 31.5, and 53.5%). This difference is statistically significant (P less than 0.01). The mean number of stenotic arteries was 1.9 +/- 0.9 in the patients without previous infarction and 2.4 +/- 0.7 in those with an infarction (P less than 0.05). Using the above-mentioned scoring system the score was 3.2 +/- 1.4 in patients without previous infarction and 4.0 +/- 1.6 in those with previous infarction (P less than 0.05). The percent myocardium threatened was 53.6 +/- 24.1 vs. 68.7 +/- 24.7 (P less than 0.01). Wall motion score was 13.8 +/- 0.6 in Group A and 10.6 +/- 3.1 in Group B (P less than 0.01), which gives values for the proportion of myocardium infarcted of 1.6 +/- 4.2 and 24.2 +/- 22.0%, respectively. The percentage still in jeopardy (after subtracting that infarcted from that threatened) was 51.8 +/- 22.7 in those without and 44.2 +/- 31.1 in those with a previous infarction: this difference is not statistically significant. We conclude that patients with unstable angina pectoris who have sustained a previous myocardial infarction have more severe coronary artery disease than similar patients without previous infarction. The amount of left ventricular myocardium still in jeopardy of becoming infarcted is, however, the same.