Oxygen Uptake Kinetics During and After Exercise are Useful Markers of Coronary Artery Disease in Patients With Exercise Electrocardiography Suggesting Myocardial Ischemia

Abstract

xercise electrocardiogram (ECG) is widely used to diagnose and evaluate the severity of patients with coronary artery disease (CAD). However, ischemia detected from the change in the ST segment of the ECG during exercise, is said to be not highly sensitive or specific. A meta-analysis on sensitivity and specificity found 68±16% in sensitivity and 77±17% in specificity. 1 For this reason, nuclear medicine stress test 2 or stress echocardiography by exercise or dobutamine 3 are used in combination in daily clinical practice. The present study is designed to increase the sensitivity and specificity for detection of myocardial ischemia by non-invasive cardiopulmonary exercise testing (CPET) in which changes in gas exchange occur consequent to exercise-induced myocardial dyskinesis, which accompanies myocardial ischemia. Editorial p 1795Recent reports have shown the usefulness of CPET for detecting myocardial ischemia in CAD patients. [4][5][6] We 4 and others 5,6 found that oxygen uptake (V • O2) failed to continue to increase linearly with increasing work rate above the anaerobic threshold (AT) or ischemic threshold during an increasing work rate CPET in CAD patients. When the left ventricular wall becomes hypokinetic, akinetic or even dyskinetic secondary to ischemia, the decreased stroke volume prevents oxygen (O2) transport to increase at a rate sufficient to supply the muscles with the O2 needed to regenerate the high energy phosphate (adenosine triphosphate (ATP)) needed by the skeletal muscles to sustain muscle contraction, aerobically. Thus V• O2 fails to increase appropriately for the increasing work rate. Because V• O2 is a product of cardiac output times the arterial-venous O2 difference, its altered kinetics reflects altered cardiac function during exercise. V • O2 kinetics at the beginning of exercise and recovery 7 reflect abrupt early changes in cardiac output at these 2 functional states, and both are slow to change in patients with congenital heart disease 8 and heart failure. 9 We hypothesized that the work rate above which myocardial (Received May 7, 2009; revised Background:The aim of the current study was to determine if the slowed exercise oxygen uptake (V • O2) kinetics, which is developed by myocardial ischemia, would be accompanied by delayed recovery V• O2 kinetics in patients with coronary artery disease (CAD). Methods and Results: Thirty-seven patients with significant ST depression during treadmill exercise underwent cardiopulmonary exercise testing with cycle ergometer. Measurements performed are the ratios of change in increase in oxygen (O2) uptake relative to increase in work rate (∆V • O2/∆WR) across anaerobic threshold (AT) and 1 mm ST depression point (ST-dep), the time constants of V • O2 during recovery (T1/2 V • O2), stress radio-isotope scintigraphy and coronary angiography. Patients were divided into CAD positive (CAD+) and CAD negative (CAD-) groups, based on coronary angiography. In CAD+, ∆V• O2/∆WR decreased above AT and ST-dep, in contrast to CAD-patients. The T1/2 V •...

Cardiopulmonary exercise testing in the early-phase of myocardial infarction

“…Therefore, the lowest values of VO 2 found in the AMIG, both in the AT and in the peak of the sub-maximal CPET, may be attributed to reduced cardiac output and increased peripheral vascular conductance. This condition may lead the patient, during exercise, to a situation of lactate accumulation and lower limb fatigue [38][39][40] , which contributes for lower exercise tolerance and possibly justify the findings of this study.…”

Left ventricular diastolic performance at rest is essential for exercise capacity in patients with non-complicated myocardial infarction

“…18 Similar to our findings, Tajama et al suggested that the decrease in VO 2 kinetics after exercise, as evidence of increased O 2 balance, is prolonged in patients after MI. 28 Our results showed that E/e 0 is strongly related to T1/2 during recovery phase. Capacity to exercise in post MI patients can be interpreted by resting Doppler-echocardiography.…”

“…26,27 The VE/VCO 2 slope is not influenced by sub-maximal exercise and beta-blocker therapy, and has complementary prognostic value to peak VO 2 . 27,28 In patients with HF, VE/VCO 2 slope has been previously correlated with cardiac output, pulmonary pressure and ventilationeperfusion mismatch. 26 Our results have shown significant correlation between VE/VCO 2 slope and E/e 0 .…”

Idiopathic pulmonary fibrosis and coronary artery disease

“…However, in the context of comprehensive care of IPF patients, an holistic approach was recently proposed [12], in which identifying and treating comorbidities, such as CAD, could be a strategy to optimize the management of the disease. In the cardiological context, CPET is a well recognized method to diagnose and/or investigate cardiovascular dysfunction (e.g., myocardial ischemia, chronic heart failure) [10,13]. With respect to lung diseases, the goal of CPET is the identification of physiopathological determinants of respiratory dysfunction as well as matching the pattern of the abnormality with the particular sites of the system involved, thus clarifying the clinical picture and possibly narrowing the differential diagnosis [14,15].…”