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PART III Iatrogenicity of Diagnostic and Therapeutic, Invasive and Noninvasive Cardiovascular Interventions, Devices, and Surgeries Ibrahim Akin Martin Borggrefe William J. Kostis STRESS MODALITIES Exercise Stress Testing In healthy individuals, physical exercise can increase myo­ car­ dial blood flow two-­to threefold via an endothelium-­ dependent flow-­ mediated pro­ cess (1). This mechanism allows to meet increased oxygen demand during exercise. In patients with significant coronary artery stenosis, myo­ car­ dial blood flow decreases during exercise (2).­ Because of ubiquitous availability, ­ simple practicality, feasibility, and cost effectiveness , exercise stress testing with ­ either treadmill or bicycle protocol is routinely used in clinical practice to rule out or confirm the existence of coronary artery disease (CAD). However, stress testing may result in overdiagnosis and overtreatment, especially with inappropriate use of testing in asymptomatic patients and patient populations with low or high pretest probability of CAD (3,4). According to current Eu­ ro­ pean Society of Cardiology (ESC) guidelines (5), exercise stress testing constitutes a valuable stress method in patients with suspected CAD and an intermediate pretest probability for CAD between 15% and 65%. Apart from ECG changes, exercise stress testing provides physicians with useful clinical information (exercise capacity, heart rate, arterial pressure during exercise) beyond just unmasking CAD. The testing also allows physicians to assess the efficacy of antianginal medi­ cation and success ­ after revascularization. In a meta-­ analysis, exercise stress testing using ST depression to define a positive test exhibited wide variability in sensitivity (mean 68%, range 23% to 100%) and specificity (mean 77%, range 17% to 100%) (6). Exercise stress testing has a number of disadvantages. False positive results are more frequent in patients with abnormal resting ECG, patients taking digitalis, or patients with left ventricular (LV) hypertrophy, intraventricular conduction abnormalities , or electrolyte disturbance. The sensitivity and specificity of exercise ECG testing is diminished in ­ women (7). Exercise stress testing does not provide information on the location and distribution of ischemia. In patients who are not able to reach at least 85% of maximum heart rate and do not experience symptoms or show significant ECG changes, the exercise test is inconclusive. Therefore, poor physical fitness, frailty, or orthopedic prob­ lems increase the risk of an equivocal test and CHAPTER 19 Iatrogenic Aspects of Noninvasive and Invasive Diagnostic Methods in Interventional Cardiology Christina Dösch, Dirk Loßnitzer, and Theano Papavassiliu 222 / Iatrogenic Aspects of Diagnostic Methods in Interventional Cardiology in patients with active bronchospasm and asthma high-­ grade atrioventricular block, hypotension, and recent (less than 24 hours) use of dipyridamole . Relative contraindications are a history of reactive airway disease, severe COPD, sick sinus syndrome, or severe sinus bradycardia (15). The application of pharmacological vasodilators is considered safe. The results from the Adenoscan Multicenter Trial Registry of 11,000 patients at 21 clinical sites shows that the negative dromotropic side effects generally do not pose a prob­ lem. Serious side effects seldom occur, and they reverse with termination of adenosine infusion (16). Dobutamine The catecholamine dobutamine, a synthetic agonist of beta-1 and beta-2 receptors, produces a two-­to threefold increase in myo­ car­ dial blood flow comparable to physical exercise and mimics exercise in increased heart rate, blood pressure, and myo­ car­ dial contractility (9). Dobutamine effects depend on the dose. At lower doses, dobutamine predominantly leads to improved contractility ; at higher doses, positive chronotropic effects are prevalent. Like adenosine, dobutamine has a short half-­ life of about two minutes, requiring continuous infusion of the drug (17). The most common noncardiac side effects are nausea, headache , tremors, shortness of breath, and anxiety (18). Nonsustained tachyarrhythmias, hypotension (greater than 30 mmHg drop in blood pressure ), and short-­ lasting bradycardias and hypertensions are known minor cardiac adverse effects of dobutamine administration (18). The occurrence of minor noncardiac and cardiac side effects increases with augmentation of the dobutamine dose and additional administration of atropine. According to a review of 26,438 dobutamine stress tests, one serious adverse event per 335 examinations occurred (18). Severe complications consisted of sustained ventricular tachycardias, myo­ car­ dial infarction (MI), and death. ­ These complications are unpredictable and not linked to symptoms or the development of dobutamine-­ induced ischemia. MI and transmural ischemia are complications that might occur as late as one hour ­ after the end of a dobutamine stress test (19). Therefore, a prolonged observation period is warranted, especially in the outpatient setting. should make the physician consider an alternative noninvasive test. Exercise stress testing should not be used in the presence of left bundle brunch block...


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