QT dispersion in the risk stratification of patients with unstable angina: correlation with clinical course, troponin T and scintigraphy.

OBJECTIVE: This study sought to evaluate the potential prognostic usefulness of QT dispersion (QTd) in patients with unstable angina. METHODS AND RESULTS: QTd was calculated and plasma troponin T (TnT) level was measured and rest perfusion imaging with Tc-99m sestamibi was performed in 62 patients admitted with chest pain at rest. All patients had a follow-up during one month in order to assess cardiac events. Cardiac events occurred in 41 patients (no deaths, 11 myocardial infarctions (MI), 4 urgent and 26 planned revascularizations). The mean QTd in patients with cardiac events was significantly higher than in those without cardiac events (68 +/- 28 vs. 54 +/- 14 ms; p = 0.01). When patients were divided into subgroups according to the cardiac events, the mean QTd in MI and revascularization were 90 +/- 25 ms and 60 +/- 25 ms, respectively. QTd in patients with MI was higher than in patients without cardiac events (p = 0.001). There was no significant difference in QTd between the revascularization subgroup and patients without cardiac events. Nineteen patients with elevated TnT had a greater QTd compared to patients with normal TnT (74 +/- 29 vs. 56 +/- 20 ms; p = 0.008). Additionally, the mean QTd in 46 patients with perfusion defects was slightly higher than in patients without (66 +/- 27 vs. 53 +/- 17 ms; p = 0.03). There was also a moderate correlation between QTd and the number of perfusion defects (r = 0.31, p = 0.01). On the other hand, most of the patients who had a MI or urgent revascularization had a QTd greater than 75 ms. CONCLUSION: The measurement of QTd in patients with unstable angina may help to stratify patients at high risk for cardiac events, in particular MI and urgent revascularization.

Acute rest perfusion imaging in high risk unstable angina: association with troponin T and clinical endpoints.

BACKGROUND: Troponin T (TnT) and rest perfusion imaging (RPI) have been reported to be important diagnostic tools for risk stratification in patients with chest pain. METHODS: We investigated the association between two methods in 60 patients presenting with typical chest pain at rest within the last 6 h before admission. All patients underwent Tc-99m gated SPECT imaging and serial TnT measurements and were followed for occurrence of adverse cardiac events up to 30 days. RESULTS: Perfusion defect was detected in 42 patients and elevated TnT was observed in 23 patients. All of the patients with an elevated TnT have also perfusion defect in RPI. Half of the patients with normal TnT level (51%) presented a perfusion defect detected by RPI (p = NS). The patients with elevated TnT levels had more perfusion defect numbers than those with normal TnT levels (8.2 +/- 2.9 vs. 5.3 +/- 2.2; p = 0.0007). Cardiac events occurred in 38 patients (14 MI, 24 revascularisation). In predicting cardiac events, RPI and TnT had sensitivities (97 vs. 58%; p < 0.001), specificities (77 vs. 95%, p = NS), positive predictive values (PPV) (88 vs. 96%; p = NS) and negative predictive values (NPV) (94% vs. 57%; p = NS), respectively. In predicting MI, the two tests had sensitivities (93 vs. 93%; p = NS), specificities (37 vs. 78%; p < 0.001), PPVs (31 vs. 57%; p = NS) and NPVs (94 vs. 97%; p = NS), respectively. CONCLUSIONS: These results suggest that in patients with rest angina (1) TnT elevation is associated with the extent of myocardial perfusion defect; (2) both tests are valuable, while positive RPI is more sensitive in predicting all cardiac events irrespective of TnT; both positive TnT and positive RPI predict a high probability to have MI; (3) both negative test results predict a very low probability to have cardiac event, including MI.

Effect of homocysteine-lowering therapy on vascular endothelial function and exercise performance in coronary patients with hyperhomocysteinaemia.

OBJECTIVE: This study was performed to determine the effect of homocysteine-lowering therapy (HLT) on endothelium-dependent vasodilation (EDD) and exercise performance in patients with coronary artery disease. METHODS AND RESULTS: Among the patients who were on the waiting list for coronary intervention, 26 male patients (plasma homocysteine (Hcy) levels > 15 micromol/l) who had a focal stenosis of at least 70% in the left anterior descending artery were included in the study. The patients were matched to receive HLT (n = 15; 0.4 mg of folic acid, 2 mg vitamin B6 and 6 microg of vitamin B12) or placebo (n = 11) until the coronary intervention was performed (mean 3.8 +/- 0.9 weeks). Brachial artery vasomotion test and treadmill stress testing were performed at baseline and 4 weeks after HLT before the time of coronary intervention in each patient. Hcy levels were found to be decreased significantly after HLT compared to baseline (23.4 +/- 6 vs. 11.3 +/- 4 micromol/l; p < 0.001) whereas placebo had no effect. HLT but not placebo produced a marked improvement in EDD, from 3.9 +/- 1.1% to 9.4 +/- 2.3% (p < 0.0001). Endothelium-independent nitroglycerin-induced dilation was similar in the HLT and placebo groups compared with the baseline. In the exercise testing, HLT resulted in a significant improvement in exercise duration and reduction in the amount of maximal ST-segment depression, (from 6.5 +/- 2 to 6.9 +/- 2 min, p = 0.02 and from 1.2 +/- 0.7 to 0.8 +/- 0.5 mm, p = 0.01, respectively) whereas placebo did not. CONCLUSION: Lowering Hcy levels improves EDD and exercise performance while reducing the exercise-induced myocardial ischaemia in patients with coronary heart disease and hyperhomocysteinaemia.