Enhanced recognition of ischemia by three variable analysis of the exercise stress test.

BACKGROUND: ECG ST-segment deviations have been the standard measure of coronary artery disease (CAD) during the exercise stress test (EST). Our past research has shown other ECG variables to be significant in EST. This study evaluates the benefit of routinely combining these variables in the detection of CAD. METHODS: Sequential patients (n = 439) with suspected CAD referred for EST had their cases reviewed. Clinical and ECG variables were associated with myocardial perfusion imaging (MPI) scintigrams used to detect ischemia during maximum EST. RESULTS: An increase in P-wave duration was the most sensitive predictor of ischemia with a sensitivity of 64.3%, a specificity of 86.5%, and a positive predictive power (PPP) of 57.8%. ST elevation ≥ 1 mm in lead AVR had a sensitivity of 53.1%, a specificity of 78.3%, and a PPP of 41.3%. ST depression ≥ 1 mm in leads V4-V6 had a sensitivity of 11.2%, a specificity of 94.7%, and a PPP of 37.9%. When these variables were combined, specificity and PPP increased to 100% (p < 0.001). CONCLUSIONS: EST evaluation solely by ST deviation fails to identify a significant portion of ischemic cases. Combinations of ΔPWD, ST elevation in AVR, and ST depression improved the identification of ischemia.

New York Heart Association functional class predicts exercise parameters in the current era.

BACKGROUND: The New York Heart Association (NYHA) functional class is a subjective estimate of a patient's functional ability based on symptoms that do not always correlate with the objective estimate of functional capacity, peak oxygen consumption (peak V(O2)). In addition, relationships between these 2 measurements have not been examined in the current medical era when patients are using beta-blockers, aldosterone antagonists, and cardiac resynchronization therapy (CRT). Using baseline data from the HF-ACTION (Heart Failure and A Controlled Trial Investigating Outcomes of Exercise TraiNing) study, we examined this relationship. METHODS: One thousand seven hundred fifty-eight patients underwent a symptom-limited metabolic stress test and stopped exercise due to dyspnea or fatigue. The relationship between NYHA functional class and peak V(O2) was examined. In addition, the effects of beta-blockers, aldosterone antagonists, and CRT therapy on these relationships were compared. RESULTS: The NYHA II patients have a significantly higher peak Vo(2) (16.1 +/- 4.6 vs 13.0 +/- 4.2 mL/kg per minute), a lower ventilation (Ve)/V(CO2) slope (32.8 +/- 7.7 vs 36.8 +/- 10.4), and a longer duration of exercise (11.0 +/- 3.9 vs 8.0 +/- 3.4 minutes) than NYHA III/IV patients. Within each functional class, there was no difference in any of the exercise parameters between patients on or off of beta-blockers, aldosterone antagonists, or CRT therapy. Finally, with increasing age, a significant difference in peak Vo(2), Ve/V(CO2) slope, and exercise time was found. CONCLUSION: For patients being treated with current medical therapy, there still is a difference in true functional capacity between NYHA functional class II and III/IV patients. However, within each NYHA functional class, the presence or absence or contemporary heart failure therapies does not alter exercise parameters.

Unconventional electrocardiographic signs of ischemia during exercise testing.

Because of the failure to consider some of the unconventional electrocardiographic signs of ischemia during exercise testing, its sensitivity and specificity are lower than optimum. Two cases are presented to illustrate how precordial peaking of the T waves and lead-strength calculations in patients with low-voltage R waves can be used to improve the diagnostic power of exercise testing. Other rarely used electrocardiographic changes during exercise testing include ST elevation in lead aVR, an increase in P-wave duration, and ST depression in premature ventricular complexes. In conclusion, this experience demonstrates that the routine consideration of these electrocardiographic changes will result in significant increases in the sensitivity and specificity of exercise testing.

Usefulness of p-wave duration to identify myocardial ischemia during exercise testing.

It is well recognized that ST-segment depression is due to subendocardial ischemia secondary to an increase in left ventricular end-diastolic pressure. The increase in left ventricular end-diastolic pressure is associated with increased left atrial pressure, resulting in left atrial wall distension that contributes to increasing P-wave duration (PWD). The objective of this study was to determine if PWD measured in leads II and V(5) during maximum exercise stress testing could be a reliable predictor of myocardial ischemia. Patients with suspected coronary disease underwent maximum exercise stress testing with myocardial perfusion imaging. PWD was measured using leads II and V(5) at rest and after exercise, with electrocardiographic complexes magnified 4 times (100 mm/s, 40 mm/mV). The change in PWD was calculated as Delta = PWD(recovery) - PWD(rest). DeltaPWD and ST-segment changes were related to the absence or presence of ischemia (localized reversible perfusion abnormalities) on myocardial perfusion imaging scans. DeltaPWD had sensitivity of 72%, specificity of 82%, negative predictive power (NPP) of 90%, and positive predictive power of 57%. ST-segment change had sensitivity of 34%, specificity of 87%, NPP of 80%, and positive predictive power of 47%. When DeltaPWD and ST changes were combined, sensitivity increased to 79% and NPP increased to 91%. In conclusion, DeltaPWD outperformed ST-segment changes in predicting myocardial ischemia on myocardial perfusion imaging scans. Furthermore, when DeltaPWD and ST-segment changes were combined, sensitivity and NPP were also significantly increased. In this study population, measuring DeltaPWD substantially increased the diagnostic value of maximum exercise stress testing.

Hyperbaric oxygen: its application in cardiology: a historical perspective and personal journey.

Hyperbaric oxygen (HBO) was first used by placing a patient with the "bends" in a pressure chamber and increasing the pressure to 3 atm with 100% oxygen. It was soon recognized that HBO could also facilitate wound healing in infected ischemic extremities. Before the pump oxygenator was developed, it was also shown to facilitate corrective surgery, especially in congenital heart disease. In 1997, after encouraging animal work, HBO therapy was used in conjunction with thrombolytics to reduce the magnitude of injury in patients with acute myocardial infarction. The benefit is probably due to the decrease in reperfusion injury, which has been shown to be a major cause of myocardial cell death when the culprit artery is opened with a catheter. The most recent development is to infuse saline saturated with HBO into the opened coronary artery immediately after angioplasty. An advantage of this treatment has been demonstrated in experimental animals and in man. Future applications of HBO treatment in cardiovascular disease await more research, but at this time it seems to have considerable promise.

Point: a prescription to decrease left ventricular function.

The Courage Trial, published in 2007, has significantly reduced the incidence of treating stable angina with angioplasty. The investigators randomized 2297 patients with documented cardiac ischemia to conservative or invasive therapy and concluded that there was no difference in major events during a follow-up of 2.5 to 7 years and that the urge to open the narrowed artery was unjustified. Over the years it has been well documented by myocardial biopsy that repeated ischemic episodes result in replacement of myocardial cells by fibrous tissue, loss of mitochondria, and deterioration of left ventricular function. Ischemic episodes often occur in the absence of angina so that it is impossible to determine whether the therapy is reducing the magnitude or duration of the process. Also, in their study, 32% of the conservatively treated patients crossed over to invasive. The evidence indicated that conservative treatment may result in a progressive decrease in left ventricular function.

Exercise hypertension: an adverse prognosis?

We sought to clarify the prognostic importance of an "exaggerated" or "hypertensive" systolic blood pressure response to exercise during an exercise test. Studies evaluating the prognosis for cardiovascular events and cardiovascular mortality in those with hypertension during exercise testing were systematically reviewed. Fourteen studies were identified. Six studies were of healthy volunteers or hypertensives. Eight studies were in subjects with known or suspected heart disease. Without established heart disease, exercise hypertension predicted cardiovascular events and cardiovascular death. However, two of the six studies included a multivariate analysis; both demonstrated no independent association. Studies in subjects with known or suspected heart disease demonstrated that exercise hypertension predicted fewer cardiac events and lesser mortality or, after multivariate adjustment, no associated risk. In a healthy population, a higher exercise blood pressure may indicate hypertension or prehypertension, instead of normal vascular function, and an associated long-term adverse prognosis. In a population with a high burden of heart disease, the highest risk subjects with the most extensive cardiac disease may not be capable of generating pressure or workload to allow the manifestation of exercise systolic hypertension. By comparison, therefore, those with exercise hypertension have a better prognosis.

Xanthine oxidase inhibitors the unappreciated treatment for heart failure.

The recognition that uric acid plays a significant role in cardiac function has been slow to be appreciated. About 50 years ago it was recognized that gout and high uric acid levels were often a marker for coronary heart disease, Since then the literature has contained several hundred studies which have demonstrated a great deal of the physiology of xanthine oxidase inhibition. A reduction in xanthine oxidase improves cardiac output, improves endothelial function, reduces myocardial infarct size, reduces inflammation, reduces myocardial oxidative stress and platelet adhesiveness. It seems logical that these effects would be beneficial to patients with congestive heart failure. A large placebo controlled trial with Allopurinol seems very likely to demonstrate that this old fashioned drug provides a new found benefit.

Significance of lead strength during exercise testing.

BACKGROUND: The aim of the study was to evaluate the contribution of relative lead strengths to exercise-induced ECG changes (ST depression) to predict the degree of myocardial ischemia as compared to the angiograms. This was accomplished by comparing the magnitude of ST depression to the ST/R ratio. Studies have shown that the diagnostic strength of a lead is directly related to the R wave amplitude and that sensitivity is significantly improved. METHODS: Three hundred patients, who underwent treadmill exercise testing and coronary angiography revealing significant coronary narrowing (> or = 70% luminal diameter narrowing), were studied, along with 150 patients clear of significant coronary artery disease (<70% luminar diameter narrowing). Our goal was to determine the correlation between the relative lead strengths, using a constructed ST/R ratio, to exercise induced ECG changes (ST depression) to predict the presence of myocardial ischemia as compared to angiographic findings. Using a cutoff of 0.1 for the ST/R ratio, our data were compared to the sensitivity and specificity of 1.0 mm ST depression. RESULTS: Overall sensitivity was improved for the ST/R ratio (84% vs 78%), while specificity was slightly decreased (81% vs 92%) in comparison to standard ST depression. When differentiating between R wave amplitudes, those with R wave < or = 10 mm showed significantly improved sensitivity (88% vs 54%) and a minor decrease in specificity (90% vs 92%). In those with R wave > or = 20 mm, the sensitivity of ST depression was higher (88% vs 71%) but the ST/R ratio was much more specific (88% vs 46%). No significant difference was observed when differentiating between male and female patients. CONCLUSION: We found that the correction of ST depression for R wave amplitude results in improved sensitivity in patients with low R waves and specificity in patients with very tall R waves (R > or = 20 mm).

The value of upsloping ST depression in diagnosing myocardial ischemia.

We evaluated the value of upsloping ST-segment depression in predicting the severity of myocardial ischemia. Comparison of the exercise electrocardiographic changes was made to myocardial perfusion images and coronary angiograms as the criteria for ischemia. We retrospectively reviewed 621 patients who underwent exercise technetium-99m tetrofosmin single photon emission computed tomography (SPECT) for the assessment of suspected or known coronary artery disease followed by coronary angiography within a 3-month period. The test sensitivity and specificity of 1 mm horizontal or downsloping ST depression in predicting reversible ischemia as assessed by gated SPECT imaging (GSI) were 65% and 87%, respectively. The corresponding values were 67% and 94% compared to coronary angiography. The sensitivity and specificity of gated SPECT imaging compared to coronary angiography were 78% and 89%. On the other hand when 1 mm upsloping ST depression at 70 ms past the J-point was regarded as abnormal, along with horizontal and downsloping, the sensitivity and specificity were 82% and 90% compared to myocardial perfusion imaging, and 77% and 92% as assessed by coronary angiography. We conclude that upsloping ST-segment depression is associated with an increased risk of coronary artery disease and is a valuable predictor of myocardial ischemia.

The severity of myocardial ischemia can be predicted by the exercise electrocardiogram.

The aim of the study was to evaluate the utility of exercise-induced ECG changes in predicting the degree of myocardial ischemia as compared to angiographic and nuclear scintigraphic images. Four hundred and seventy one patients in whom exercise nuclear scintigraphy and coronary angiography revealed significant coronary narrowing (> or =70% luminal diameter narrowing) were studied. Down-sloping ST depression was found to be the best predictor of a large area of reversible ischemia (RI). Time of resolution of ST depression was the second most powerful predictor and the time of onset of ST depression was the third best predictor. RI on nuclear scintigraphy correlated better than angiographic findings with the ECG changes.