Andreas P. Michaelides

Exercise-induced QRS prolongation in patients with coronary artery disease: A marker of myocardial ischemia

The objective of this study was to investigate the effect of myocardial ischemia on the QRS duration in patients with coronary artery disease since acute myocardial ischemia decreases conduction velocity through the ischemic myocardium and may produce QRS prolongation on the surface electrocardiogram. One hundred fifty patients who underwent cardiac catheterization and exercise radionuclide ventriculography within 1 month of each other were studied. Forty patients had normal coronary arteries and 110 had coronary artery disease. QRS duration decreased with exercise in patients with normal coronary arteries (-3.0 msec, confidence limits -6.2 to 0.2), but increased in patients with coronary artery disease; exercise-induced QRS prolongation was directly related to the number of diseased vessels (4.8 msec in patients with one, 7.8 msec in patients with two, and 13.3 msec in patients with three-vessel disease, p < 0.001). Likewise, QRS duration decreased with exercise in patients without exercise-induced segmental contraction abnormalities (-1.8 msec, confidence limits -3.7 to 0.1), but increased in patients with segmental contraction abnormalities (6.7 msec in patients with one, 13.5 msec in patients with two, and 21 msec in patients with three segmental contraction abnormalities, p < 0.0001). Exercise-induced QRS prolongation was better related to the number of segmental contraction abnormalities than to the number of diseased vessels (p < 0.01). It was concluded that exercise produces QRS prolongation in patients with coronary artery disease in direct relation to the number of diseased vessels and to exercise-induced segmental contraction abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Improved myocardial performance during repetitive exercise testing: The role of extracellular superoxide dismutase activity in a model of exercise-induced myocardial preconditioning

BACKGROUNDnThe aim of this study was to investigate whether endogenous antioxidant defense is involved in adaptation to myocardial ischemia in patients with coronary artery disease and severe exercise-induced myocardial ischemia.nnnMETHODSnFifty patients, aged 50 to 72 years (mean, 58 +/- 6 years), with positive exercise test results underwent 4 treadmill exercise tests. Thallium-201 scintigraphy was performed during the first and the fourth testing. The second, the third, and the fourth tests were performed the next day. The time interval between the second and the third test was 15 minutes, and between the third and the fourth test, the interval was 45 minutes. Extracellular superoxide dismutase activity was measured just before and at the peak of the first and the fourth exercise test.nnnRESULTSnThe patients were divided in 2 groups according to the extent of myocardial ischemia at peak exercise of the fourth test compared with the first test. Most of the patients studied (37/50) showed improved myocardial performance during the last of the sequential exercise tests, as demonstrated with the studied exercise parameters and the extent of myocardial ischemia in thallium-scintigraphy. Extracellular superoxide dismutase activity before the last exercise test was found to be significantly increased only in the patients who had improved myocardial performance at the last of the sequential exercise tests.nnnCONCLUSIONnThe beneficial effects of sequential episodes of exercise-induced myocardial ischemia seem to be strongly related to extracellular superoxide dismutase activity. Although there is still lack of direct evidence, our data support the theory that the favorable adaptation to repetitive exercise may represent an aspect of the clinical relevance of ischemic preconditioning in humans.

Impact of abnormal nocturnal blood pressure fall on vascular function

BACKGROUNDnIt is well known that nondipping pattern of arterial hypertension has a harmful effect on target organs such as the brain, heart, and kidneys. However, it remains uncertain whether abnormal dipping patterns of nocturnal blood pressure (BP), such as extreme and reverse dipping, influence vascular function.nnnMETHODSnThis study comprised consecutive 2800 individuals (1554 men and 1246 women). All were nondiabetic and had uncomplicated, untreated essential sustained hypertension based on office measurements. After a 2-week wash-out period, 24-h ambulatory BP recordings were obtained and patients were classified by their nocturnal systolic BP fall (132 extreme dippers with >20% nocturnal systolic BP fall; 1235 dippers with >10% but <20% fall; 1146 nondippers with >0% but <10% fall; and 287 reverse dippers with <0% fall). Microalbumin, ACR (albumin/creatinine ratio), and microglobulin values were measured in all groups.nnnRESULTSnExtreme dippers did not differ from dippers with regard to microalbumin, microglobulin excretion, or ACR. On the contrary, reverse dippers had significantly (P <.0001) higher values, compared with nondippers, for microalbumin (49.5 v 37.2 mg/dL), microglobulin (10.33 v 8.71 mg/dL), ACR (104.9 v 65.2), and percentages of abnormal values for these parameters.nnnCONCLUSIONSnMicroalbuminuria, an index of vascular function, differentiates reverse dippers from nondippers, but not extreme dippers from dippers among hypertensive patients.

Exercise duration as a determinant of vascular function and antioxidant balance in patients with coronary artery disease

Background Exercise improves the clinical outcome of patients with coronary artery disease (CAD); however, the ideal exercise duration for each patient remains unclear. Objective To investigate the effects of exercise duration on arterial elastic properties and antioxidant/pro-oxidant mechanisms in patients with CAD. Design, setting, patients, interventions Sixty male patients with CAD were randomised into two groups, and underwent exercise for 30 min or 60 min in a crossover design with 2 weeks wash-out period. In all participants aortic and radial blood pressures (BP) and arterial elastic properties (augmentation index (AIx)/pulse wave velocity (PWV)) were determined at baseline and 24 h after exercise. Plasma malonyldialdehyde (MDA) and superoxide dismutase (SOD)1 and SOD2 levels were also measured. Results Exercise had no effect on aortic and radial BP (p=NS for all). Walking for 30min improved AIx (from 33.79±0.91% to 31.73±0.86%, p<0.001) and PWV (from 9.26±0.95m/s to 9.06± 0.21m/s, p<0.001), while exercise for 60min had adverse effects on vascular stiffness (for AIx: from 33.37± 0.93% to 33.73± 1.05%, p=NS and for PWV: from 9.25±0.19m/s to 9.37±0.21m/s, p<0.05 mainly in older patients). Exercise for 60min was associated with a significant 20% increase in MDA levels (p<0.05). Exercise had no effects on SOD1 levels, however it significantly increased SOD2 levels after 30min (from 2.26±0.22ng/mL to 2.36±0.18ng/mL, p<0.05) but not after 60min (p=NS). Conclusion Shorter exercise duration was associated with favourable antioxidant and vascular effects, while longer exercise blunted these beneficial effects and was accompanied by adverse effects on vascular function, mainly in older coronary patients. Further studies are required to explore the hypothesis that a more individualised approach to the selection of the appropriate exercise programme should be considered for patients with CAD.

Significance of QRS Duration Changes in the Evaluation of ST-Segment Depression Presenting Exclusively During the Postexercise Recovery Period

Background: The aim of this study was to evaluate the contribution of QRS prolongation in the diagnosis of coronary artery disease (CAD) in patients with exercise‐induced ST‐segment depression exclusively during the recovery period.

Correlation of modification of heart rate recovery with adaptation to myocardial ischemia in a model of sequential exercise testings.

Background: Heart rate recovery (HRR) has been identified as a reliable predictor of cardiac mortality, correlated with autonomic tone. In a model of sequential exercise testings, we investigated the reproducibility of HRR and the association between HRR modification and myocardial adaptation to ischemia.

Detection of Multivessel Disease Post Myocardial Infarction Using an Exercise‐Induced QRS Score

Objective:u2002The aim of this study was to investigate the ability of Athens QRS score values to detect stenoses in other coronary arteries than the obstructed ones (which caused the myocardial infarction [MI]) in patients with a history of MI.

945-66 Combination of Left and Right Precordial Leads: A New Technique in Exercise Testing with the Highest Diagnostic Ability for the Detection of Coronary Artery Disease

It is known that right precordial leads RV 3 , RV 4 , RV 5 could detect Rightcoronary (RC) artery stenosis. The common exercise test (ET) has a low ability to detect RC disease especially as a single vessel disease (VD). The aim of this study was to improve the diagnostic accuracy of the ET for the detection of coronary artery disease (CAD) using a combination of Left (L) and Right (R) precordial leads. We studied 133 patients (pts) aged 32–73 (mean 48xa0±xa07) years (122 males and 11 females) who underwent treadmill ET using the Bruce protocol and coronary arteriography. We used two Exercise systems. The pts were walking on the treadmill of the one system. In the monitor of the first system the usual 12-lead ECG and in the monitor of the second system the additional R precordial leads (RV 3 , RV 4 , RV 5 ) were simultaneously recording. The start and the end of the ET in both systems were done at the same time by two of the investigators. Thirty-four pts had normal coronary arteries, whereas 54 pts had l-VD, 27 2-VD and 18 3-VD. Of the pts with 1VD, 25 had Left Anterior Descending (LAD) disease, 16 had RC artery disease and 13 Left Circumflex (LC) artery disease. The sensitivies of the usual 12- lead ET and of the combination of Land R precordial leads (new technique) for the detection of LAD disease were found respectively 76% (19/25) vs 92% (23/25), for RC disease 25% (4/16) vs 88% (14/16), for LC diseese 47% (6/13) vs 85% (11/13), for the detection of l-VD were 54% (29/54) vs 89% (48/54), for 2-VD 63% (17/27) vs 96% (26/271. for 3-VD 83% (15/18) vs 100% (18/18) and for the detection of CAD 61% (61/99) vs 93% (92/99), Pxa0lxa00.001, while the specificities were found the same 91% (31/34) Conclusion It is concluded that this new technique based on two Exercise Systems has the highest diagnostic ability for the detection of CAD and it evokes the need for the creation of a new exercise system with 15 leads

Novel methodology for the detection of exercise-induced myocardial wall motion abnormalities by surface electrocardiogram during exercise test.

BACKGROUNDnWe investigated whether ischemia-induced wall motion abnormalities during exercise test modify electrical vector variation.nnnMETHODSnWe performed treadmill exercise test and thallium 201 scintigraphy in 150 normotensives. Beat-to-beat change of direction of S wave in V(1) (reference lead) was compared with that of R wave in V(5) and aVF, representative of anterior and inferior walls, respectively. The percentage of neighboring QRS couples where S wave in V(1) and R wave in V(5) or aVF change toward the same direction (increase or decrease) constitutes V1-V5 and V1-aVF indexes.nnnRESULTSnV1-V5 and V1-aVF indexes were significantly decreased in subjects with reversible anterior or inferior ischemia, respectively. A decrease in V1-V5 index ≥0.14 defines those with anterior wall ischemia (sensitivity, 100%; specificity, 75.5%), whereas a decrease in V1-aVF index ≥0.05 defines those with inferior wall ischemia (sensitivity, 92.3%; specificity, 61.5%).nnnCONCLUSIONSnThese novel electrocardiographic exercise test indexes improved significantly their sensitivities.