Quantitative and qualitative analysis of the relationship between exercise-induced R wave amplitude changes and severity of coronary artery disease

The correlation between R wave voltage variations (delta R) and the angiographic severity of coronary artery disease (CAD) at progressively increasing heart rate (HR) steps was evaluated in 51 patients (pts) without CAD (OV), in 42 pts with single (SVD), in 43 with double (DVD) and in 59 pts with triple vessel disease (TVD). At the end of stress the sensitivity of delta R was higher in DVD and TVD pts than in SVD pts. There was no clear correlation between exercise-induced R wave changes and the angiographic severity of CAD, since the qualitative and quantitative delta R evaluation during effort showed similar changes in delta R for a wide range of HR's in the entire study population. Since different degrees of exercise tolerance were found in pts with SVD, DVD and TVD, we hypothesize that the correlation between delta R and the severity of CAD at the end of stress testing may be artifactual.     

Heart rate adjustment of ST-segment depression for reduction of false positive electrocardiographic responses to exercise in asymptomatic men screened for coronary artery disease

The ability of heart rate (HR) correction of exercise-induced ST-segment depression (the delta ST/HR index) to reduce the number of false positive exercise electrocardiograms during initial screening for occult coronary artery disease (CAD) was examined in active, asymptomatic men from the Army Reserve. Among 606 consecutive men given treadmill tests, 62 asymptomatic subjects with normal results on resting electrocardiograms but abnormal outcomes on standard exercise electrocardiograms underwent rest and exercise radionuclide cineangiography, and the 10 subjects with abnormal radionuclide findings then underwent coronary angiography. A previously established delta ST/HR index less than 1.6 microV/beat/min correctly identified 34 of 52 subjects (65%) who, despite abnormal standard exercise electrocardiographic findings, had no rest or exercise radionuclide abnormalities. A delta ST/HR index greater than or equal to 1.6 microV/beta/min detected 7 of 7 subjects with abnormal radionuclide cineangiograms who had CAD at cardiac catheterization, but also identified 2 of 3 subjects with an abnormal radionuclide test who had no CAD. In contrast to the 7 of 62 subjects (11%) with abnormal standard exercise test criteria who had radionuclide and angiographic evidence of CAD, a delta ST/HR index partition of 1.6 microV/beat/min separated subjects into subgroups with 0% (0 of 35) vs 26% (7 of 27) prevalences of CAD by serial diagnostic evaluation (p less than 0.01). Thus, among asymptomatic subjects with abnormal electrocardiographic responses to exercise, simple HR correction of the magnitude of ST-segment depression reduced by 56% the number of subjects with standard exercise test criteria leading to referral for additional diagnostic evaluation, without loss of sensitivity for angiographically proven CAD and with accurate negative predictive value.(ABSTRACT TRUNCATED AT 250 WORDS)     

Correlation between exercise test and coronariography]

In order to evaluate the sensibility and specificity of the maximal treadmill exercise-stress test, a correlation was made, in fifty patients, of the resus of the test and the findings at selective coronary arteriography. None of the patients had received cardioactive drugs previous to the study. Among twenty-nine patients with proven coronary disease, three had false negative exercise tests. The remaining twenty-six cases had positive tests. The sensitivity of the method (reliability in identifying the presence of disease) was 89.7%. Twelve of twenty-one subjects with normal coronary arteries had negative exercise tests. In eight patients without coronary artery lesions, the exercise test was positive (false positive tests). An additional patient had an equivocal response and is included among the false positive responses. These nine-patients form a special group since they had severe heart disease, even though it was not due to atherosclerosis of the major coronary vessels. The specificity of the test (reliability in identifying the absence of disease) was 57.1%. However, in the absence of other heart disease, none of the subjects with normal coronary arteries had a false positive response. An analysis is made of the possible causes of these false negative and false positive responses. It was also shown in this study that the patients with coronary artery disease and positive treadmill tests had a definite functional aerobic impairment as well as a significant reduction in such indices of myocardial oxygen consumption as the heart rate and the double product (pressure-pulse), when compared to the subjects with normal coronary vessels and negative tests. In the group of patients with false positive responses, these parameters were not significantly different from the normals. The exercise-stress test protocol used in this study appears to have an adequate sensibility and an acceptable specificity.     

P-R interval in relation to heart rate during exercise and the influence of posture and autonomic tone

P-R interval (PR) in relation to heart rate (HR) during exercise was studied in healthy men. When subjects were in a recumbent position, mean PR between HR 90–140 beats/min (bpm) decreased linearly from 167±8 ms to 136±5 ms. (Regression line: PR=0.287 HR +182.9, r=0.40). PR did not decrease further at HR up to 180 bpm. When subjects were in a sitting position, a further decrease occurred after HR 150–160 bpm. The shortest PR observed during exercise was 100 ms. The decrease of PR between HR 90–140 bpm was affected by atropine but not by propranolol. Higher HR was not achieved after propranolol, and after atropine there was no difference in PR in either exercise position compared to the two exercises without any drug. Thus, exercise induces a decrease in PR which is for the most part completed at HR 140–150 bpm and is mainly achieved by a withdrawal of the parasympathetic tone. PR at HR 90 bpm was correlated to body surface area, indicating that the PR duration is related to the body and heart dimensions.     

Comparison of platelet function during exercise in normal subjects and coronary artery disease patients: Potential role of platelet activation in myocardial ischemia

Platelet function parameters as influenced by exercise stress were evaluated in 22 patients with coronary artery disease (CAD) and in 13 normal subjects. Upon exercise stress, 14 CAD patients exhibited positive tests and eight exhibited negative tests. Platelet counts during exercise increased similarly in normal and CAD patients. Platelet aggregation response to ADP was unaffected by exercise both in normal and CAD patients. Platelets from 7 of the 14 CAD patients with positive stress tests had increased sensitivity to endoperoxide analog (U-46619) defined as less than 200 ng/ml U-46619 required for 50% platelet aggregation. Resting plasma beta-thromboglobulin (B-TG) levels, an index of in vivo platelet activation, were significantly higher in CAD patients compared to normal subjects (74 +/- 7 and 41 +/- 5 ng/ml, respectively; p less than 0.02). During exercise plasma B-TG levels increased in normal subjects to 60 +/- 5 ng/ml. In contrast, B-TG levels increased to 102 +/- 14 ng/ml in CAD patients (p less than 0.01 compared to normal subjects). These increases were transient and B-TG declined to preexercise values soon after exercise. Eleven of the 12 CAD patients with positive exercise stress tests had increases in plasma B-TG levels, whereas only three of the eight CAD patients with negative stress tests had any increase. These observations of increased platelet activation in certain CAD patients during exercise may be related to exercise-induced myocardial ischemia.     

Heart rate adjustment of ST depression in patients with coronary disease and negative standard exercise tests

Heart rate (HR) adjustment of ST depression (STD) has been shown to correctly classify exercise test findings in up to 85% of normal subjects and patients with “equivocal” electrocardiographic (ECG) responses (≥ 100 μV upsloping STD), but the performance of these methods in patients with truly negative ECG responses (<100 μV STD) has not been examined in detail. We reviewed negative standard exercise ECGs in 54 men and women (mean age 61 years) with coronary disease, comprising 16% of consecutive treadmill tests that were performed in 337 patients with angiographic coronary artery disease or stable angina. Mean STD was only 63 ± 21 μV (0.63 mm) in these negative tests. Despite these subthreshold values for STD, the ST/HR index was abnormal (≥1.6 μV/bpm) in 27 of 54 patients (50%) when STD was adjusted for the change in HR during exercise. Compared with patients with normal values for HR-adjusted STD, patients with an abnormal ST/HR index were slightly older (64 vs. 58 years, P <0.05) and demonstrated a trend toward lower exercise duration (10.0 vs. 11.8 min). An abnormal ST/HR index was associated with greater subthreshold STD (73 vs. 53 μV, P < 0.0005) and smaller HR change (35 vs. 56 bpm, P < 0.0001) with exercise. Among the 27 patients with a normal ST/HR index by simple HR adjustment, 11(44%) had abnormal ST/HR slopes (≥2.4 μV/bpm) by the more complex linear regression method. Therefore, HR adjustment of STD contributes to the improved sensitivity of the exercise ECG by correct classification of some patients with truly negative standard tests. The magnitude of subthreshold STD and the extent of HR change with exercise both contribute to improved test performance. The increased sensitivity afforded by HR adjustment of STD highlights the importance of the precise measurement of subthreshold STD that is afforded by computerized ECG during exercise testing.     

Abnormal heart rate recovery after exercise as a reflection of an abnormal chronotropic response

Abnormal decline in heart rate (HR) after exercise has been linked to increased cardiac mortality. This study compares the decrease in HR in different patient types, elucidates the relation between the increase and decrease of HR with exercise, and studies the role of beta blockers on the recovery of HR after exercise. One hundred patients with coronary artery disease (CAD), 50 subjects with a very low likelihood of CAD (normals), and 21 postcardiac transplant (Tx) patients underwent Bruce protocols. Peak HR, percent of peak HR achieved, HR reserve percent, and decline in HR at 1, 3, 5, and 8 minutes were obtained for all groups and also for subgroups based on the use of beta blockers. HR recovery at 1, 3, 5, and 8 minutes differed significantly between patients with CAD, normals, and Tx patients. HR recovery at 1, 3, 5, and 8 minutes also differed significantly within the groups (normal and CAD) based on the use of beta blockers. There was highly significant correlation between decrease in HR and peak HR, percent peak HR and HR reserve percent in normal and CAD groups. After correction of the HR recovery for dependence on peak HR and HR reserve percent, the difference in HR recovery between normal and CAD groups was markedly reduced. The difference in the decrease of HR within each group (normal and CAD), based on the use of beta blockers or not, was also markedly reduced. beta blockers have a significant impact on the decrease in HR due to its effect on chronotropism. HR recovery rate is highly dependent on the chronotropic response. Hence, the main portion of the abnormality in HR recovery after exercise can be explained by chronotropic incompetence.     

Functional evaluation of sympathetic and parasympathetic system in Chagas' disease using dynamic exercise

Ten normal subjects and 14 patients with chronic Chagas' disease (seven with and seven without heart disease) underwent dynamic exercise on a cycle ergometer. Heart rate (HR), pulmonary ventilation (V), oxygen consumption (VO2), carbon dioxide production (VCO2), and respiratory quotient (RQ) were measured. Increasing workloads (25, 50, 100, and 150 W) were applied for 4 min and intercalated with resting periods. The main objective of this protocol was to analyse heart rate response in relation to the other cardiorespiratory variables in order to evaluate the functional conditions of the sympathetic and parasympathetic cardiac efferents. Analysis of the results showed that (a) the group of chagasic patients with heart disease had lower heart rates (p less than 0.05) than normal subjects during the initial 10 s (delta HR 0-10 s) of effort (fast component); (b) the difference between the normal subjects and chagasic patients without heart disease was not statistically significant; (c) the abnormalities in heart rate response were due to depression of parasympathetic efferent action on the sinus node; (d) the slow heart rate response (delta HR 1-4 min), which expresses the degree of sympathetic stimulation of the sinus node, was comparable in the three groups studied, thus showing unimpaired adrenergic responses during dynamic exercise in Chagas' disease; and (e) the V, VO2, VCO2, and RQ values were normal at all workloads in each group, suggesting that vagal dysfunction does not affect oxygen transport at these submaximal levels of dynamic exercise.     

The usefulness of exercise-induced QRS axis shift as a predictor of coronary artery disease

The QRS axis of 101 patients with coronary artery disease (CAD) and 57 normal subjects without CAD who underwent coronary arteriograms were measured before and after exercise testing. There was no improvement in the sensitivity of positive axis shifts (15 degrees or greater) for CAD (18%) when compared to the value of positive ST depression (61%). However, the specificity of positive axis shifts for CAD was significantly increased (98%) when compared to the value of positive ST depression (77%). In addition, 39% of those patients with CAD (39 of 101) showed false negative ST depression, but 18% of these patients (7 of 39) showed a positive axis shift. In normal subjects 21% (12 of 57) showed false positive ST depression, but all of the 21% (12 of 12) showed negative axis shift. There was no significant difference in the increments of heart rate between positive ST depression, positive axis shift, and negative ST depression, negative axis shift. No statistical differences in the sensitivity of ST depression and an axis shift for one-, two- and three-vessel diseases were noted. The specificity of left-axis shift for the left anterior descending artery lesion was 98% and the specificity of right-axis shift for the right coronary artery and/or left circumflex artery lesion was 91%. Therefore, the axis shift response is no more sensitive for the detection of CAD than ST depression. However, when a positive axis shift is observed, one can predict two things: the CAD and the localization of the coronary stenosis.     

The Interplay of Exercise Heart Rate and Blood Pressure as a Predictor of Coronary Artery Disease and Arterial Hypertension

J Clin Hypertens (Greenwich). 2012;00:00–00. ©2012 Wiley Periodicals, Inc. Delayed blood pressure (BP) and heart rate (HR) decline at recovery post‐exercise are independent predictors of incident coronary artery disease (CAD). Delayed BP recovery and exaggerated BP response to exercise are independent predictors of future arterial hypertension (AH). This study sought to examine whether the combination of two exercise parameters provides additional prognostic value than each variable alone. A total of 830 non‐CAD patients (374 normotensive) were followed for new‐onset CAD and/or AH for 5 years after diagnostic exercise testing (ET). At the end of follow‐up, patients without overt CAD underwent a second ET. Stress imaging modalities and coronary angiography, where appropriate, ruled out CAD. New‐onset CAD was detected in 110 participants (13.3%) whereas AH was detected in 41 former normotensives (11.0%). The adjusted (for confounders) relative risk (RR) of CAD in abnormal BP and HR recovery patients was 1.95 (95% confidence interval [CI], 1.28–2.98; P=.011) compared with delayed BP and normal HR recovery patients and 1.71 (95% CI, 1.08–2.75; P=.014) compared with normal BP and delayed HR recovery patients. The adjusted RR of AH in normotensives with abnormal BP recovery and response was 2.18 (95% CI, 1.03–4.72; P=.047) compared with delayed BP recovery and normal BP response patients and 2.48 (95% CI, 1.14–4.97; P=.038) compared with normal BP recovery and exaggerated BP response individuals. In conclusion, the combination of two independent exercise predictors is an even stronger CAD/AH predictor than its components.     

Systolic time-interval evaluation by thermistor plethysmography during uninterrupted dynamic stress test in normals and in patients with coronary artery disease

18 patients with coronary artery disease (CAD) and 21 normal subjects underwent a triangular bicycle exercise test. Systolic time intervals (STI) were calculated at rest and every 2 min during exercise. Under resting conditions, STI were similar in the two groups. During exercise, the ejection time index (ETI), i.e. left ventricular ejection time (LVET) corrected for HR, rose significantly more in CAD patients, as compared to normals. Pre-ejection period (PEP) was also differently affected by exercise in CAD patients, who showed a more shortened PEP (p less than 0.001) in the early stage of dynamic stress. PEP/LVET ratio, which in the control group decreased continuously, in CAD patients fell during exercise at lower work loads (p less than 0.001), whilst rose during strenuous exercise. Finally, significant differences (p less than 0.001) were found in the percent change (% delta) PEP/LVET ratio between the two groups during the early phase of exercise, in which no superimposition of single values was present. Therefore, this last parameter seems the most reliable to differentiate clearly CAD patients from normal subjects, but its use must be limited at early exercise.     

The early ergometric test after myocardial revascularization]

Ergometric tests (ET) were used to study 900 patients undergoing surgical myocardial revascularisation during the period between January 1983 and December 1989. ET was carried out without medical therapy between the 30th and 35th day post surgery. The test was positive in 193 subjects (21%); in 42 of the latter (5% of the total and 229 of positive subjects) symptoms of effort angina were found to persist. ET was negative in 557 patients (62%); 150 subjects (17%), although not positive, did not attain a sufficient heart rate to enable a 100% negative diagnosis to be made. No major complication was observed. Maximal short-term ET is a reliable and safe test for checking the efficacy of myocardial revascularisation and to assess functional recovery. In view of the relatively high percentage of positive tests due to ischemia but with the complete absence of symptoms, the authors affirm that the mere onset of anginous symptoms alone cannot be considered indicative of the success of cardiosurgery.     

Diagnostic usefulness of the post-exercise systolic blood pressure response for the detection of coronary artery disease in patients with diabetes mellitus

Patients with diabetes mellitus (DM) often have a positive result on exercise testing despite a normal coronary arteriogram, which indicates that exercise-induced ST depression is not always an accurate indicator of the presence of coronary artery disease (CAD) in such patients. The present study evaluated the usefulness of the post-exercise systolic blood pressure (SBP) response for the detection of CAD in 47 consecutive patients with DM. Significant stenotic lesions were detected by angiography in 25 patients; 18 of these had true positive (TP) exercise testing results, and 7 had false negative (FN) results. No significant stenotic lesions were detected in the remaining 22 patients and of these 10 had true negative (TN) exercise testing results, and 12 had false positive (FP) results. The SBP ratio (SBP after 3 min of recovery divided by the SBP at peak exercise) was significantly higher in patients with coronary stenoses than in those without. Analysis of the relative cumulative frequency revealed that a SBP ratio greater than 0.87 was associated with significant stenoses. The sensitivity, specificity, and accuracy of ST change combined with a SBP ratio greater than 0.87 for detecting stenoses in patients with DM were 68%, 82%, and 74%, respectively. These results suggest that calculating the SBP ratio, in combination with monitoring for ST depression, improves the accuracy of treadmill exercise testing for the detection of CAD in patients with DM.     

冠心病患者运动试验中QRS波时间变化

观察了42例踏车试验阳性的冠心病人及20例踏车试验阴性的正常人踏车运动试验前后QRS波时间的变化，结果显示，正常人踏车即刻2、4、分钟QRS波时间较踏车前明显缩短（P均＜0．05）。冠心病组踏车后即刻、2、4、6分钟较踏车前显著延长（P均＜0．05），ST段明显压低者，QRS波时间延长更显著，提示冠心病患者运动致QRS时间延长是心肌缺血的一个标志。     

Pulmonary thallium uptake: correlation with systolic and diastolic left ventricular function at rest and during exercise

Quantified pulmonary 201-thallium uptake, assessed as pulmonary/myocardial ratios (PM) and body surface area-corrected absolute pulmonary uptake (Pc), was determined from single photon emission computed tomography studies in 22 normal subjects and 46 consecutive patients with coronary artery disease (CAD). By means of equilibrium radionuclide angiography (ERNA), ejection fraction (EF), peak ejection rate (PER) in end-diastolic volume (EDV/sec) and peak filling rate (PFR) in EDV/sec and stroke volume (SV/sec) units, PFR/PER ratio, and time to peak filling rate (TPFR) in milliseconds were computed at rest and during exercise (n = 35). Left ventricular response to exercise was assessed as delta EF, relative delta EF, delta EDV, and delta ESV. In normal subjects the PM ratios showed significant inverse correlation with PER at rest and with EF, PER, and PFRedv during exercise. For the left ventricular response to exercise, delta ESV showed significant correlation with the PM ratios. The body surface area-corrected pulmonary uptake values showed no correlation with any of the variables. In patients with CAD the PM ratios and Pc uptake showed significant inverse correlation with EF, PER, PFRedv and to exercise EF, exercise PER, and exercise PFRedv. For the left ventricular response to exercise, delta EF showed significant inverse correlation with the PM ratios but not with the Pc uptake. Neither in normal subjects nor in patients with CAD did any of the independent diastolic variables show significant correlation with the PM ratios or Pc values. Thus pulmonary thallium uptake is correlated with systolic left ventricular function at rest and during exercise in normal subjects and in patients with CAD but not with diastolic function. In normal subjects delta ESV and in patients with CAD, delta EF showed correlation with pulmonary thallium uptake.     

Analysis of exercise-induced changes in R wave amplitude in asymptomatic men with electrocardiographic ST-T changes at rest

Fifty asymptomatic men, 44 (88 percent) of whom were pilots or allied aviation personnel, were referred because of resting ST-T electrocardiographic changes indistinguishable from those of myocardial ischemia. Because of the nature of their occupations, cardiac catheterization was performed to establish the presence or absence of coronary artery disease. Exercise tests were performed and analyzed retrospectively with respect to exercise-induced changes in the S-T segment and R wave amplitude. The results were correlated with coronary angiographic and echocardiographic findings.The 50 subjects were classified into two groups: Group I, 5 men with angiographically proved coronary artery disease, and Group II, 45 men without significant coronary arterial obstruction. Analysis of the S-T segment changes at peak exercise showed 21 subjects (42 percent) with a positive exercise test and 29 (58 percent) with a negative test. All subjects in Group I had a positive test. Sixteen subjects (35 percent) in Group II had a false positive result. Analysis of exercise-induced changes in R wave amplitude revealed that six subjects had a positive R wave response on the basis of sum of the changes in voltage in the leads measured (Δ∑R). Four of the six subjects had coronary artery disease and the other two were thought to have a cardiomyopathy. One subject with coronary artery disease had a negative R wave response. Echocardiography revealed five subjects with asymmetric septal hypertrophy; two of these had a positive exercise test and three a negative test on the basis of S-T segment criteria.Thus, symptom-limited treadmill exercise testing of asymptomatic men with resting ST-T electrocardiographic changes produced a high incidence rate of false positive results when S-T segment criteria were used, whereas analysis of changes in R wave amplitude yielded only two false positive results, both in men who had evidence of other heart disease.     

Identification of false positive exercise tests with use of electrocardiographic criteria: a possible role for atrial repolarization waves

Atrial repolarization waves are opposite in direction to P waves, may have a magnitude of 100 to 200 mu V and may extend into the ST segment and T wave. It was postulated that exaggerated atrial repolarization waves during exercise could produce ST segment depression mimicking myocardial ischemia. The P waves, PR segments and ST segments were studied in leads II, III, aVF and V4 to V6 in 69 patients whose exercise electrocardiogram (ECG) suggested ischemia (100 mu V horizontal or 150 mu V upsloping ST depression 80 ms after the J point). All had a normal ECG at rest. The exercise test in 25 patients (52% male, mean age 53 years) was deemed false positive because of normal coronary arteriograms and left ventricular function (5 patients) or normal stress single photon emission computed tomographic thallium or gated blood pool scans (16 patients), or both (4 patients). Forty-four patients with a similar age and gender distribution, anginal chest pain and at least one coronary stenosis greater than or equal to 80% served as a true positive control group. The false positive group was characterized by 1) markedly downsloping PR segments at peak exercise, 2) longer exercise time and more rapid peak exercise heart rate than those of the true positive group, and 3) absence of exercise-induced chest pain. The false positive group also displayed significantly greater absolute P wave amplitudes at peak exercise and greater augmentation of P wave amplitude by exercise in all six ECG leads than were observed in the true positive group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Heart rate adjustment of exercise-induced ST segment depression. Improved risk stratification in the Framingham Offspring Study

BACKGROUND. Simple heart rate adjustment of ST segment depression during exercise (delta ST/HR index) and the pattern of ST depression as a function of heart rate during exercise and recovery (the rate-recovery loop) have been shown to improve the ability of the exercise electrocardiogram to detect the presence of coronary heart disease (CHD), but the performance of these methods for the prediction of future coronary events remains to be examined. METHODS AND RESULTS. We compared the delta ST/HR index and the rate-recovery loop with standard electrocardiographic criteria for prediction of CHD events in 3,168 asymptomatic men and women in the Framingham Offspring Study who underwent treadmill exercise electrocardiography and who, at entry, were free of clinical and electrocardiographic evidence of CHD. After a mean follow-up of 4.3 years, there were 65 new CHD events: four sudden deaths, 24 new myocardial infarctions, and 37 incident cases of angina pectoris. When a Cox proportional hazards model with adjustment for age and sex was used, a positive exercise electrocardiogram by standard criteria (greater than or equal to 0.1 mV horizontal or downsloping ST segment depression) was not predictive of new CHD events (chi 2 = 0.40, p = 0.52). In contrast, stratification according to the presence or absence of a positive delta ST/HR index (greater than or equal to 1.6 microV/beat/min) and a positive (counterclockwise) rate-recovery loop was associated with CHD event risk (chi 2 = 9.45, p less than 0.01) and separated subjects into three groups with varying risks of coronary events: high risk, when both tests were positive (relative risk 3.6; 95% confidence interval, 2.4-5.4); intermediate risk, when either the delta ST/HR index or the rate-recovery loop was positive (relative risk, 1.9; 95% confidence interval, 1.3-2.8); and low risk, when both tests were negative. After multivariate adjustment for age, sex, smoking, total cholesterol level, fasting glucose level, diastolic blood pressure, and electrocardiographic evidence of left ventricular hypertrophy, the combined delta ST/HR index and rate-recovery loop criteria remained predictive of coronary events (chi 2 = 5.45, p = 0.02). CONCLUSIONS. Heart rate adjustment of ST segment depression by the delta ST/HR index and the rate-recovery loop during exercise electrocardiography can improve prediction of future coronary events in asymptomatic men and women.     

Long-term prognostic value of resting heart rate in patients with suspected or proven coronary artery disease.

AIMS: Heart rate reduction is the cornerstone of the treatment of angina. The purpose of this study was to explore the prognostic value of heart rate in patients with stable coronary artery disease (CAD). METHODS AND RESULTS: We assessed the relationship between resting heart rate at baseline and cardiovascular mortality/morbidity, while adjusting for risk factors. A total of 24 913 patients with suspected or proven CAD from the Coronary Artery Surgery Study registry were studied for a median follow-up of 14.7 years. All-cause and cardiovascular mortality and cardiovascular rehospitalizations were increased with increasing heart rate (P<0.0001). Patients with resting heart rate > or =83 bpm at baseline had a significantly higher risk for total mortality [hazard ratio (HR)=1.32, CI 1.19-1.47, P<0.0001] and cardiovascular mortality (HR=1.31, CI 1.15-1.48, P<0.0001) after adjustment for multiple clinical variables when compared with the reference group. When comparing patients with heart rates between 77-82 and > or =83 bpm with patients with a heart rate < or =62 bpm, the HR values for time to first cardiovascular rehospitalization were 1.11 and 1.14, respectively (P<0.001 for both). CONCLUSION: Resting heart rate is a simple measurement with prognostic implications. High resting heart rate is a predictor for total and cardiovascular mortality independent of other risk factors in patients with CAD.     

Relationship between insulin resistance assessed by HOMA-IR and exercise test variables in asymptomatic middle-aged patients with type 2 diabetes

We investigated the relationship between index of insulin resistance (IR) and exercise test variables in middle-aged asymptomatic patients with Type 2 diabetes. METHODS: 90 patients (48 men, 42 women; age: 49 +/- 6 yr) were included in the study. We used homeostasis model assessment for IR (HOMA-IR) index as index of IR. All patients were subjected to treadmill exercise test. Four subjects were tested positive (4.4%). Study patients were separated into three groups: group I (no.=26) HOMA-IR index <2.24; group II (no.=26) index 2.24-3.59; group III (no.=38) index >3.59. RESULTS: group I had less frequency of cardiovascular risk factors than group II and III (p=0.001). Systolic blood pressure baseline as well as peak exercise values, were higher in group III than in group I and II (p=0.048 vs p=0.01, respectively). Higher total exercise time and peak workload were found in group I than group II and III (p=0.04). The recovery of heart rate (delta HR(pr)) was similar among the study groups. We found significant negative correlations between HOMA-IR and total exercise time and peak workload. In addition we found significant negative correlations between age vs chronotrophic index (CI), delta HR(pr), and peak workload. There were also similar negative correlations between duration of diabetes vs CI and delta HR(pr). CONCLUSIONS: IR is associated with a variety of cardiovascular risk factors. Some exercise test variables point out changes of autonomic tone during exercise in elevated IR group. Negative correlation between HOMA-IR and peak exercise capacity (METs) may well confirm increased mortality in hyperinsulinemia.