R wave amplitude during exercise. Relation to left ventricular function and coronary artery disease

Repurposing Combination Therapy of Voacamine With Vincristine for Downregulation of Hypoxia-Inducible Factor-1α/Fatty Acid Synthase Co-axis and Prolyl Hydroxylase-2 Activation in ER+ Mammary Neoplasia

The current study investigated the role of combination therapy with voacamine and vincristine in preventing mammary gland carcinoma through prolyl hydroxylase-2 activation. Prolyl hydroxylase-2 activation leads to the downregulation of hypoxia-inducible factor-1α and fatty acid synthase. Overexpression of hypoxia-inducible factor-1α and fatty acid synthase has been previously reported in solid tumors of the mammary gland. After screening a battery of natural compounds similar to vincristine, voacamine was selected as a possible prolyl hydroxylase-2 activator, and its activity was evaluated using a 7,12-dimethylbenz[a]anthracene-induced rat model. The combination therapy was evaluated for cardiac toxicity using a hemodynamic profile. Angiogenic markers were evaluated by carmine staining. Monotherapy and combination therapy were also evaluated for liver and kidney toxicity using hematoxylin and eosin staining. The antioxidant potential was delineated using oxidative stress markers. The serum metabolomic profile was studied using NMR spectroscopy, and the disruption of fatty acids was evaluated using gas chromatography. Western blotting of proteins involved in hypoxic pathways was performed to decipher the action of therapy at the molecular level. Immunoblotting analysis validated that combination therapy has potential toss with prolyl hydroxylase-2 activity and thus initiates proteolytic degradation of hypoxia-inducible factor-1α and its consequent effects. Combination therapy also stimulated programmed cell death (apoptosis) in rapidly dividing cancer cells. The present study explored the role of voacamine inactivation of prolyl hydroxylase-2, which can decrease the overexpression of hypoxia-inducible factor-1α and fatty acid synthase in mammary gland carcinoma cells.

Validation of the Polar V800 heart rate monitor and comparison of artifact correction methods among adults with hypertension

Heart rate variability (HRV) measurements via ambulatory monitors have become common. We examined the validity of recording R-R intervals using the Polar V800^™ compared to 12-lead electrocardiograms (ECG) among middle-aged (44.7±10.1years); overweight to obese (29.8±4.3 kg.m^-2) adults (n = 25) with hypertension (132.3±12.2/ 84.3±10.2 mmHg). After resting for 5-min in the supine position, R-R intervals were simultaneously recorded using the Polar V800^™ and the 12-lead ECG. Artifacts present in uncorrected (UN) R-R intervals were corrected with the Kubios HRV Premium (ver. 3.2.) automatic (AC) and threshold-based (TBC) correction, and manual correction (MC) methods. Intra-class correlation coefficients (ICC), Bland-Altman limits of agreement (LoA), and effect sizes (ES) were calculated. We detected 71 errors with the Polar V800^™ for an error rate of 0.85%. The bias (LoAs), ES, and ICC between UN and ECG R-R intervals were 0.69ms (-215.80 to +214.42ms), 0.004, and 0.79, respectively. Correction of artifacts improved the agreeability between the Polar V800^™ and ECG HRV measures. The biases (LoAs) between the AC, TBC, and MC and ECG R-R intervals were 3.79ms (-130.32 to +137.90ms), 1.16ms (-92.67 to +94.98ms), and 0.37ms (-41.20 to +41.94ms), respectively. The ESs of AC, TBC, and MC were 0.024, 0.008, and 0.002, and ICCs were 0.91, 0.95, and 1.00, respectively. R-R intervals measured using the Polar V800^™ compared to 12-lead ECG were comparable in adults with hypertension, especially after the artifacts corrected by MC. However, TBC correction also yielded acceptable results.

Augmentation of Electrocardiographic QRS R-Amplitude Precedes Radiocontrast-Induced Hypotension during Mobile Computed Tomography Scanning

Although intravenous administration of contrast media may trigger a variety of adverse reactions, sedated patients undergoing computed tomography (CT) scanning usually are not able to report their symptoms, which may delay detection of adverse reactions. Furthermore, changes in vital signs cannot be typically measured during mobile CT scanning, which worsens the situation. We aimed to characterize contrast-related hemodynamic changes that occur during mobile CT scanning and predict sudden hypotension based on subtle but robust changes in the electrocardiogram (ECG). We analyzed the digitized hemodynamic data of 20 consecutive patients who underwent clipping of a cerebral artery aneurysm and contrast-enhanced CT scanning following the surgical procedure. Hemodynamic variables, including ECG findings, invasive blood pressure (BP), pulse oximetry results, capnography findings, cardiac output, and systemic vascular resistance, were monitored simultaneously. We measured morphological changes in ECG-derived parameters, including the R-R interval, ST height, and QRS R-amplitude, on a beat-to-beat basis, and evaluated the correlation between those parameters and hemodynamic changes. After the radiocontrast injection, systolic BP decreased by a median 53 mmHg from baseline and spontaneously recovered after 63 ± 19 s. An increase in QRS R-amplitude (median 0.43 mV) occurred 25 ± 10 s before hypotension developed. The receiver operating characteristic curve showed that a 16% increase in QRS R-amplitude can predict a decrease in systolic BP of >25% (area under the curve 0.852). Increased cardiac output (median delta 2.7 L/min from baseline) and decreased systemic vascular resistance (median delta 857 dyn·s/cm⁵ from baseline) were also observed during hypotension. During mobile CT scanning, profound but transient hypotension can be observed, associated with decreased vascular resistance. Augmentation of QRS R-amplitude from an ECG represents a sensitive surrogate for onset of a hypotensive episode after contrast injection, thereby serving as a simple and continuous noninvasive hemodynamic monitoring tool.

Interaction between renin-angiotensin and sympathetic nervous systems in a rat model of pressure overload cardiac hypertrophy

1 A raised cardiac workload activates neurohormones which will increase muscle mass and shift contractility to the right along the Frank-Starling curve. 2 This study examined the interaction between the SNS and RAS in contributing to vascular responsiveness following the development of cardiac hypertrophy due to aortic banding. 3 Sprague Dawley rats (180-200 g) were assigned to one of six groups; Normal, Sham-operated, Aortic Banded (AB), Aortic Banded treated with losartan (ABLOS), Aortic Banded treated with 6-hydroxydopamine (ABSYMP) and Aortic banded treated with both losartan and 6-hydroxydopamine (ABSYMPLOS). A constricting band was placed around the supra renal aorta on day zero with drug treatment from day 37 to day 44. Vasopressor responses to noradrenaline, phenylephrine, methoxamine and angiotensin II were measured on day 45. 4 The magnitudes of the MAP responses to all vasoactive agents, expressed as percentage changes, were similar in Normal and Sham groups, but reduced in the AB group. ABLOS group showed attenuated response to ANGII whereas all responses were enhanced in the ABSYM group. 5 A positive interaction between the two systems was observed with alpha(1A)-adrenoceptors identified as a major component of SNS and AT(1) receptors of RAS to induce vasopressor effects.

Endurance exercise promotes cardiorespiratory rehabilitation without neurorestoration in the chronic mouse model of parkinsonism with severe neurodegeneration

Physical rehabilitation with endurance exercise for patients with Parkinson's disease has not been well established, although some clinical and laboratory reports suggest that exercise may produce a neuroprotective effect and restore dopaminergic and motor functions. In this study, we used a chronic mouse model of Parkinsonism, which was induced by injecting male C57BL/6 mice with 10 doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (25 mg/kg) and probenecid (250 mg/kg) over 5 weeks. This chronic parkinsonian model displays a severe and persistent loss of nigrostriatal neurons, resulting in robust dopamine depletion and locomotor impairment in mice. Following the induction of Parkinsonism, these mice were able to sustain an exercise training program on a motorized rodent treadmill at a speed of 18 m/min, 0 degrees of inclination, 40 min/day, 5 days/week for 4 weeks. At the end of exercise training, we examined and compared their cardiorespiratory capacity, behavior, and neurochemical changes with that of the probenecid-treated control and sedentary parkinsonian mice. The resting heart rate after 4 weeks of exercise in the chronic parkinsonian mice was significantly lower than the rate before exercise, whereas the resting heart rate at the beginning and 4 weeks afterward in the control or sedentary parkinsonian mice was unchanged. Exercised parkinsonian mice also recovered from elevated electrocardiogram R-wave amplitude that was detected in the parkinsonian mice without exercise for 4 weeks. The values of oxygen consumption, carbon dioxide production, and body heat generation in the exercised parkinsonian mice before and during the Bruce maximal exercise challenge test were all significantly lower than that of their sedentary counterparts. Furthermore, the exercised parkinsonian mice demonstrated a greater mass in the left ventricle of the heart and an increased level of citrate synthase activity in the skeletal muscles. The amphetamine-induced, dopamine release-dependent locomotor activity was markedly inhibited in the sedentary parkinsonian mice and was also inhibited in the exercised parkinsonian mice. Finally, neuronal recovery from the loss of nigrostriatal tyrosine hydroxylase expression and dopamine levels in the severe parkinsonian mice after exercise was not evident. Taken all together, these data suggest that 4 weeks of treadmill exercise promoted physical endurance, resulting in cardiorespiratory and metabolic adaptations in the chronic parkinsonian mice with severe neurodegeneration without demonstrating a restorative potential for the nigrostriatal dopaminergic function.

ECG variable cine: computer program for presentation of temporal changes in ECG variables over different number of ECG leads

The analysis of exercise electrocardiogram (ECG) is based on the alteration of the measured variables in the detection of coronary artery disease (CAD). In its existing form the analysis of the exercise ECG is laborious and requires much time. The temporal analysis of the ECG variable and the comparison between different phases of the exercise test is difficult and time consuming, especially the simultaneous examination of the variables over several leads. In this article we present a computer program, ECG Variable Cine, for the visualization of the temporal changes of values of exercise ECG variables over the selected ECG lead system. The program includes the stationary 3-D presentation for the variables' alteration simultaneously in all selected leads over the time of exercise test. In addition, the program determines two parameters; the average value of the variable over the selected leads at every sample moment, and the chronotropic index, a parameter that indicates heart rate response to exercise. According to the results the average value of ST-segment deviation at the end of the exercise over the leads and chronotropic index are clinically more competent than the maximum value of ST-segment depression in the detection of CAD.

Comparison of ST-segment/heart rate slope analysis with standard ST-segment measurement criteria to outcome of exercise thallium-201 imaging

We compared standard ST-segment analysis and ST/HR slope analysis of exercise ECG studies with reference to outcome of exercise thallium-201 studies in 341 patients. Sensitivity was significantly better using ST/HR slope compared with standard ST analysis. Specificity was not significantly different.

Significance of R wave changes in exercise-induced supraventricular extrasystoles. Angiographic correlates

To evaluate the clinical significance of observed R wave amplitude changes in exercise-induced supraventricular extrasystoles in comparison to the preceding sinus beat, 94 patients catheterized for possible coronary artery disease (CAD) were studied. Significant CAD was documented in 63 patients--34 with myocardial infarction (group A1) and 29 without (group A2)--whereas 31 patients had normal coronary arteries or coronary lesions less than 30% (group B). All patients underwent treadmill stress testing using the Bruce protocol within a month after cardiac catheterization. R wave amplitude increased or remain unchanged in extrasystole (R(x-s) > or = 0) in patients with CAD, while it decreased (negative R(x-s) in patients without significant CAD (P < .0001). In patients with CAD R(x-s) values were positively related to the number of obstructed coronary arteries (P < .01), while no significant difference was found between groups A1 and A2. The correlations of R wave amplitude changes in extrasystoles were significant with coronary obstruction score values (r = .82 and .85 in groups A1 and A2, respectively) and with left ventricular ejection fraction values (r = -.88, -.86 and -.90 in groups A1, A2, and B, respectively). R(x-s) > or = 0 value had a sensitivity of 79% and a specificity of 90% for CAD detection, while sensitivity was higher (89%) and specificity was lower (57%) for the prediction of left ventricular dysfunction. It is concluded that R(x-s) > or = 0 value is indicative of CAD, multivessel disease, and poor left ventricular performance, while its negative value is combined with minimal or no CAD and normal ejection fraction values.

Changes in the QRS segment during exercise: effects of acute beta-blockade with propranolol

Changes in the QRS complex during exercise may provide information with respect to ischaemic heart disease. The intention with present investigation was to shed light on mechanisms behind QRS changes and to study the possibly confounding effects of beta-blockade on such alterations with exercise. Placebo or propranolol respectively was infused in randomized and double-blinded order in seven young healthy men before a maximum exercise test. Advanced computerized vectorcardiography and impedance cardiography was recorded continuously together with blood pressures and blood samples. The Y-lead magnitude increased significantly with propranolol infusion (P < 0.05), but it tended to decrease in the Z-lead (P < 0.07). While the serum potassium concentrations increased (P < 0.0005), the spatial QRS magnitude tended to decrease irrespective of treatment (P < 0.07). These changes correlated with changes in QR-duration (adj r2 > 0.58). With exercise, the mean spatial QRS magnitude decreased with similar amounts irrespective of treatment. However, propranolol made the magnitude decrease earlier (P < 0.01). No effect of treatment was detected on the decrease in QRS-duration. Immediately after exercise, the QRS complex continued to change as during exercise in the placebo investigations, but did not with propranolol (P < 0.05). These different patterns were most obvious in the first half of the QRS complex in the Y-lead. It is concluded that acute beta-blockade modifies QRS alterations both during and after exercise in healthy subjects. This indicates that such drugs may have confounding effects in evaluations of the diagnostic value of QRS alterations.

Prognostic value of changes in R-wave amplitude during exercise testing after a first acute myocardial infarction

To investigate the prognostic value of exercise-induced changes in R-wave amplitude and their relation to other exercise and angiographic variables, 303 consecutive patients who underwent maximal exercise testing and coronary angiography within 2 months of a first acute myocardial infarction were studied. R-wave amplitude at peak exercise increased or was unchanged in 159 patients (57.4%) and decreased in 118 (42.6%). Increased R-wave amplitude was significantly related to underlying 3-vessel disease (p = 0.0001), the extent of ST-segment depression on exercise (p = 0.0001), and the time to 1 mm ST depression (p less than 0.05). Follow-up information was available in 285 patients (86.4%) at a mean of 4 +/- 1.8 years. Death from cardiac causes occurred in 25 patients (9%); 18 (6.5%) developed recurrent myocardial infarction, and 32 (11.6%) developed angina. Variables with a predictive value for cardiac death were maximal exercise heart rate (p = 0.0005), occurrence of exercise-related supraventricular arrythmia (p = 0.02), and number of diseased vessels (p = 0.02). R-wave changes had no predictive value. No variable had a predictive value for recurrent infarction. Maximal exercise heart rate (p = 0.02) and increased R-wave amplitude (p = 0.0001) were significantly related to the occurrence of angina at follow up. Exercise-related R-wave increases were associated with the presence of angina at follow-up, but had no predictive value for cardiac death or recurrent infarction; their association with subsequent angina appears to reflect an association with more severe underlying coronary disease.

Ischaemic heart disease and the changes in the QRS and ST segments during exercise: a pilot study with a novel vectorcardiographic system

In order to find new ischaemic parameters, the spatial changes of the Frank vectorcardiogram were continuously analysed with a new, highly precise vectorcardiographic method during, and immediately after a maximal exercise test. This was done in 18 young healthy males, and 18 patients with scintigraphic reversible ischaemia. During exercise, different patterns between the groups were noted for the changes in the mean QRS magnitude in the Y-lead (P less than 0.005), the QRS-integral (P less than 0.05), and the QRS-duration (P less than 0.05). Immediately after exercise, several QRS parameters in the normal group continued to change according to the same pattern as during exercise (P less than 0.05), which was in contrast with the patterns of the ischaemic group (P less than 0.01). The spatial ST difference at J+20 ms discriminated well between the groups, especially when corrected for QRS-magnitudes at rest and heart rate (P less than 0.0005). In short, this pilot study supports previous findings in that changes in amplitude and duration of the QRS complex during exercise discriminated between healthy young males and patients with ischaemic heart disease. Moreover, rapid discriminating changes were seen in the QRS segment during cessation of exercise. These changes deserve attention since they may be of importance for the conflicting results on the diagnostic value of QRS changes during exercise.

Changes in the electrocardiographic response to exercise in healthy women

Changes in the P wave, QRS complex, ST segment, and T wave during and after maximal exercise were quantitatively analysed in 116 healthy women with a mean age of 39. The corrected orthogonal Frank lead electrocardiogram was continuously recorded and computer processed during bicycle ergometry. With exercise, maximal spatial P wave vectors shifted downward. The Q wave amplitude became more negative and the R wave amplitude diminished considerably in leads X and Y: the S wave amplitude decreased only slightly in these leads. The QRS vectors shifted towards right and posteriorly during exertion and a further shift in the same direction was seen in the recovery period. The ST segment amplitude 60 ms after the J point decreased with exertion and became negative at heart rates above 140 beats per minute, in particular in lead Y. ST segment depression increased with age. The T wave amplitude decreased during exercise and increased sharply in the recovery period. Though mean R wave amplitude in leads X and Y became more negative with exercise, this response was unpredictable in individual women. The exercise induced changes in QRS vectors in women resembled those described in men. Changes in the amplitude of the R wave should not be used for the diagnosis of coronary disease in women. ST segment depression was more pronounced in the inferiorly oriented lead Y than in lead X but it was unrelated to changes in the QRS vectors in these leads.

New coronary artery disease index based on exercise-induced QRS changes

Exercise-induced changes in Q, R, and S wave amplitudes have been reported to detect coronary artery disease but with low specificity, low sensitivity, or both; it was hypothesized that their incorporation into a composite index (Athens QRS score) might improve specificity and sensitivity. For this purpose 246 patients were analyzed retrospectively and 160 prospectively. All patients underwent maximal exercise testing with a standard Bruce protocol and coronary arteriography as part of the diagnostic evaluation for possible or definite coronary artery disease. The Athens QRS score was decreased as the number of obstructed coronary arteries increased (normal coronary arteries = 7.85 +/- 5.23 mm, one-vessel disease = 5.2 +/- 5.3 mm, two-vessel disease = -0.85 +/- 5.4 mm, three-vessel disease = -3.5 +/- 5.8 mm; p less than 0.0001); the score was unrelated to exercise-induced ST segment depression, and negative (less than 0) scores were always associated with coronary artery disease. An Athens QRS score of 5 mm predicted coronary artery disease with sensitivity ranging from 75% to 86% and a specificity ranging from 73% to 79%, values higher than those of the Q wave (75% and 50%, respectively), R wave (65% and 55%), and S wave (70% and 10%) and of the ST segment depression (62% and 70%). It is concluded that exercise-induced changes in the QRS complex provide a useful index not only for the diagnosis but also for the assessment of severity of coronary artery disease.

Exercise-induced ST segment depression in the diagnosis of multivessel coronary disease: a meta analysis

To evaluate the variability in the reported accuracy of the exercise electrocardiogram (ECG) for predicting severe coronary disease, meta analysis was applied to 60 consecutively published reports comparing exercise-induced ST depression with coronary angiographic findings. The 60 reports included 62 distinct study groups comprising 12,030 patients who underwent both tests. Both technical and methodologic factors were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity 81% [range 40% to 100%, SD 12%]; mean specificity 66% [range 17% to 100%, SD 16%]). All three variables found to be significantly and independently related to sensitivity were methodologic (the exclusion of patients with right bundle branch block, the comparison with another exercise test thought to be superior in accuracy and the exclusion of patients taking digitalis). Exclusion of patients with right bundle branch block and comparison with a "better" exercise test were both significantly associated with sensitivity for the prediction of triple vessel or left main coronary artery disease. Adjustment of exercise-induced ECG changes for changes in heart rate was strongly associated with the specificity for critical disease (partial R2 = 0.436, p = 0.0001).

Exercise-induced ST depression in the diagnosis of coronary artery disease. A meta-analysis

To evaluate the variability in the reported diagnostic accuracy of the exercise electrocardiogram, we applied meta-analysis to 147 consecutively published reports comparing exercise-induced ST depression with coronary angiography. These reports involved 24,074 patients who underwent both tests. Population characteristics and technical and methodologic factors, including publication year, number of electrocardiographic leads, exercise protocol, use of hyperventilation, definition of an abnormal ST response, exclusion of certain subgroups, and blinding of test interpretation were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity, 68%; range, 23-100%; SD, 16%; and mean specificity, 77%; range, 17-100%; SD, 17%). The four study characteristics found to be significantly and independently related to sensitivity were the treatment of equivocal test results, comparison with a "better" test such as thallium scintigraphy, exclusion of patients on digitalis, and publication year. The four variables found to be significantly and independently related to specificity were the treatment of upsloping ST depressions, the exclusion of subjects with prior infarction or left bundle branch block, and the use of preexercise hyperventilation. Stepwise linear regression explained less than 35% of the variance in sensitivities and specificities reported in the 147 publications. There is wide variability in the reported accuracy of the exercise electrocardiogram. This variability is not explained by information reported in the medical literature.

Local conduction delay causes R-wave amplitude increase in patients with effort angina

Eighty-seven unipolar electrocardiograms distributed over the entire thorax were simulataneously recorded before and after treadmill exercise in 43 patients. Exercise-induced R-wave amplitude change (delta R) and peak R time (time from the onset of QRS to the peak of R wave), were calculated for each lead. The maximal delta R of 87 leads was designated as the max delta R. After exercise, regional delay of peak R time (greater than or equal to 10 msec) on the chest was observed in 13 patients. These patients had significantly higher max delta R than those without such regional peak R time delay (0.71 +/- 0.31mV vs. 0.33 +/- 0.20mV, p less than 0.01). In each case, the site of peak R time delay was almost the same as the site of max delta R. There was no significant difference in the peak heart rate, rise of the systolic blood pressure (delta BPs) during exercise or extent of ischemic ST depression between patients with and without peak R time delay. We concluded that ventricular condition delay plays an important role in the increase of R-wave amplitude after exercise in patients with effort angina pectoris.

Exercise electrocardiographic variables: a critical appraisal

To compare four recently proposed methods of analyzing the exercise electrocardiogram with the conventional analysis of ST segment depression, 303 consecutive patients without myocardial infarction who had been referred for coronary arteriography underwent stress electrocardiography and stress thallium imaging. The specificity for the prediction of a greater than 50% coronary obstruction of 0.5, 1.0, 1.5 and 2.0 mm ST segment depression measured in the conventional way was 0.59, 0.73, 0.88 and 0.94, respectively. The specificity of a thallium perfusion defect was 0.79. Sensitivities of the conventional ST depressions, thallium defect, the change in the sum of the R amplitudes and the slope adjusted for heart rate increase were calculated and compared at the cited levels of specificity. R wave changes had a significantly lower sensitivity than did the conventionally analyzed ST depression at each level of specificity. Slope-adjusted ST depression had a slightly higher sensitivity than that of conventional ST depression only at a specificity of 0.73 (0.68 versus 0.65, p = 0.07). R wave-adjusted ST depression was significantly more sensitive than conventional ST depression only at a specificity of 0.94 (0.45 versus 0.36, p = 0.01). Heart rate-adjusted ST depression was more sensitive than conventional ST depression at all of the specificities except 0.59. This pattern of superior accuracy of heart rate-adjusted ST depressions was preserved for the prediction of multivessel coronary disease. Heart rate adjustment is a simpler and more accurate modification of the conventional electrocardiographic analysis than are the other three methods studied.

Directional variability in the R wave response during serial exercise testing in patients with coronary artery disease

The reproducibility of the direction of R wave amplitude response to exercise was analyzed in patients with coronary artery disease. Forty-three serial exercise tests were performed by 10 patients with exertional angina pectoris and documented coronary artery disease (CAD). Seventeen tests (37%) resulted in no change or an increase in R wave amplitude (abnormal response). Twenty-six tests (63%) resulted in a decrease in R wave amplitude. The direction of the R wave amplitude response was variable in at least one exercise test in 7 of 10 patients with CAD, all of whom had reproducible ischemic ST segment responses during serial testing. The inconsistent R wave response in these patients was unrelated to heart rate, workload, or duration of exercise. Because of the variability in the directional R wave response during serial exercise testing in CAD patients, we conclude that the R wave response during exercise is unreliable for the detection of CAD or ischemia-related myocardial dysfunction.

On the clinical value of conventional and new exercise electrocardiographic criteria: a comparative study

We have evaluated the clinical value of new electrocardiographic criteria in exercise testing. In this study, we compared both ST-segment and R-wave amplitude criteria, separately and in combination with the findings from coronary arteriography in 122 patients. In these selected patients application of conventional ST-segment criteria gave a sensitivity of 31% and a specificity of 100%; with application of the slow upsloping ST-segment criteria the sensitivity was 51% and the specificity 82%. Analysis of R-wave amplitude changes alone led to a sensitivity of 50% and a specificity of 61%. In combined interpretation of ST-segment and R-wave amplitude changes the sensitivity was 51% and the specificity 93%. We conclude that slow upsloping ST-segment criteria constitute the most important recent improvement in interpreting exercise test results and that the value of R-wave amplitude changes during exercise in diagnosing significant coronary artery disease is rather low in the individual patient. R-wave amplitude changes, however, may have value in patients with a previous myocardial infarction and in reducing false-negative and false-positive responses according to ST-segment criteria. Combined interpretation of ST-segment and R-wave amplitude criteria is useful but not very efficient.

R-wave amplitude responses to rapid atrial pacing: a marker for myocardial ischemia

Atrial pacing-induced changes in the sum of R-wave amplitude were measured in leads V5, X, Y, and Z at rates of 100 bpm (phase I), 150 bpm (phase II), and immediately after pacing (phase III) in 33 patients undergoing cardiac catheterization for evaluation of chest pain. Seventeen (51%) patients showed evidence of ischemia during atrial pacing (typical anginal pain and/or at least a 1 mm ST-segment depression) and 16 (49%) showed no evidence of ischemia. Mean R-wave amplitude changes from baseline in the ischemic patients were: phase I: -8% (p = not significant), phase II: +3% (p = not significant), and phase III: +13% (p less than 0.01); and in nonischemic patients: phase I: -11% (p less than 0.02), phase II: -18% (p less than 0.01), and phase III: +2% (p = not significant). These two distinct patterns of R-wave amplitude changes were highly sensitive (85%), specific (92%), and predictive (92%) for identifying patients with myocardial ischemia but did not correlate (p = not significant) with either the angiographically determined extent of coronary artery obstructive disease (CAD), resting left ventricular function, or the dynamic, atrial pacing-induced changes in left ventricular dimensions determined by M-mode and two-dimensional echocardiography. Thus, R-wave amplitude changes induced by atrial pacing can be used to identify patients with myocardial ischemia independent of coronary anatomy or resting left ventricular function.(ABSTRACT TRUNCATED AT 250 WORDS)

Improving diagnostic accuracy of the exercise test by combining R-wave changes with duration of ST segment depression in a simplified index

To enhance the reliability of the exercise test in diagnosing both overall coronary artery disease and multivessel coronary artery disease, a discriminant function was obtained by means of stepwise linear discriminant analysis. Both electrocardiographic and nonelectrocardiographic factors were used to derive the discriminant function in a retrospective group of 231 patients, 168 of whom had angiographically defined coronary artery disease. The discriminant function converted into a simple exercise index or score was then applied to a retrospective group of 120 patients, 98 of whom had coronary artery disease. This index, combining R-wave changes with duration of ST segment depression and patient's sex, proved highly accurate in diagnosing coronary artery disease in male patients and in diagnosing the absence of coronary artery disease in female patients. When compared to standard ST segment criteria, the sensitivity and predictive value of the exercise index was significantly higher.

Factors influencing R wave amplitude in patients with ischaemic heart disease

R wave amplitude changes during exercise have been ascribed to alteration in left ventricular volume and their measurement advocated for the improved diagnosis of coronary disease. The reproducibility of exercise QRS changes and their relation to ST segment depression, respiratory pattern, and left ventricular volume during ischaemia were studied in 10 patients with angina and coronary disease. QRS amplitude was measured in a 16 lead precordial map during three identical exercise tests in each patient and left ventricular volume assessed continuously using gated blood pool imaging with a single scintillation probe during manoeuvres to provoke ischaemia. During exercise, QRS amplitude increased or remained unchanged in four patients and fell in six patients in a consistent manner for each patient. R wave amplitude was not affected by changes in respiratory pattern. R wave amplitude did not alter in 33 of 39 episodes of left ventricular volume increase (mean 32%) or decrease (mean 36%) in end-diastolic counts. These findings suggest that precordial R wave changes during ischaemia are not determined primarily by alteration in left ventricular volume or the respiratory pattern. Though reproducible in each patient and following a definite relation to ST segment depression, the variable directional response during exercise suggest that R wave amplitude changes have little diagnostic value.

Influence of R wave analysis upon diagnostic accuracy of exercise testing in women

Exercise electrocardiography in women with chest pain is associated with a high incidence of false positive ST segment depression. The recent observation that changes in R wave amplitude during exercise can also be used diagnostically may improve the value of stress testing in women. The results of 12 lead treadmill exercise and coronary angiography were reviewed in 62 women, mean age 51 years, presenting with "angina" without previous myocardial infarction. These were compared with exercise results in 14 healthy asymptomatic volunteers with a mean age of 26 years. In addition to conventional ST analysis, R wave amplitude changes during exercise, measured in leads II, III, a VF, and V4 to 6, were examined. While the sensitivity and specificity of ST and R wave changes were similar at about 67%, their combined interpretation was helpful. If both ST and R wave criteria were negative the predictive accuracy for normal coronary angiography was 94% (17/18). Alternatively, in tests showing both ST depression and an abnormal R wave response, coronary angiography was always abnormal (13/13). None of the normal volunteers developed ST segment depression and 93% (13/14) had a normal R wave response. If both were positive, however, coronary angiography was always abnormal (13/13). Although stress test interpretation in women is difficult, R wave analysis is a useful adjunct to ST change and can improve the predictive accuracy of the test in a significant number of patients.

Inability of exercise-induced R wave changes to predict coronary artery disease

To determine the value of exercise-induced R wave changes in diagnosing coronary disease 200 patients undergoing coronary angiography were studied with 16 lead precordial exercise mapping. R wave amplitude was calculated before and immediately after exercise as the sum of R in all 16 leads, the sum of the R waves in the left plus the S waves in the right precordial leads, as well as the sum of the R waves only in those leads that manifested S-T depression. Coronary artery disease was found in 154 patients, S-T depression developed in 122 (sensitivity 79 percent); the sum of R increased or remained unchanged in 61 and decreased in 93 (sensitivity 40 percent). Forty-six patients did not have coronary artery disease; S-T depression developed in 5 (specificity 89 percent); the sum of R increased or was unchanged in 30 and decreased in 16 (specificity 35 percent). Similar results were obtained using the other criteria for calculating R wave amplitude. Exercise-induced S-T depression was identified in 5. 1 +/- 2.6 (mean +/- standard deviation) of the 16 precordial leads and in 2.0 +/- 1. 1 of the chest leads of the standard electrocardiogram (p less than 0.01). Thus, electrocardiographic alterations found in the standard chest leads represent only a small variable proportion of the total projection. When the whole precordial area was analyzed, R wave changes were so unpredictable that they could not be used in the diagnosis of coronary disease.

Nocturnal hypoxemia and associated electrocardiographic changes in patients with chronic obstructive airways disease

To study the direct effects of nocturnal hypoxemia on the heart, we recorded electrocardiographic tracings and arterial oxygen saturation (SaO2) during the night in patients with chronic obstructive airways disease. In seven "blue-bloater" patients the mean basal SaO2 was less than 80 per cent, and it fell by more than 10 per cent during 29 episodes of transient hypoxemia. Only five such episodes occurred in three of five "pink-puffer" patients. All "blue bloaters" with low basal mean SaO2 had multiple atrial and ventricular premature contractions and a high heart rate at rest; six patients has a prolonged QTc, three had ST-T depression, and one had right-bundle-branch block. Oxygen therapy increased basal mean SaO2, reduced ectopic activity, abolished ST-T changes and bundle-branch block, significantly reduced the resting heart rate and the amplitude of the R and S waves, and shortened the QTc in four nonsmokers. These results suggest that sustained hypoxemia contributes to myocardial dysfunction and heart failure in "blue-bloater" patients.