Block IV - 2.pdf

Advanced ECG Diagnostic Block IV Prepared by Khulud Al-Johani  Exercise electrocardiogram (ECG) union a a well-validated procedure for establishing the diagnosis and prognosis of coronary heart disease, as well as assessing exercise...

Advanced ECG Diagnostic Block IV Prepared by Khulud Al-Johani  Exercise electrocardiogram (ECG) union a a well-validated procedure for establishing the diagnosis and prognosis of coronary heart disease, as well as assessing exercise capacity (ie, functional capacity) , also known as stress testing. www.m.m ima The exercise ECG indirectly detects myocardial ww ischemia, which is the physiologic consequence of a mismatch between the supply and demand for blood. For those unable to perform sufficient physical exertion to adequately complete an exercise ECG test, or when specific clinical conditions exist , pharmacological stress testing with vasodilators or dobutamine is indicated. ws osaimsuaa.wsw siai dkws mamoiia.m.Eco www.iow.im Schematic representation of the relative development of the manifestations of myocardial ischemia as the rate-pressure product is increased. Regional myocardial dysfunction, which can be detected as regional wall motion abnormalities on echocardiography, occurs before ECG changes or anginal chest pain. Pathophysiologic Considerations disease Fins coronary Umm in The exercise stress ECG test has two major purposes: 1) To determine the capability of the coronary circulation to increase oxygen delivery to the myocardium in response to an increased demand. o During physical exertion, myocardial oxygen demand is increased by the increase in systolic blood pressure (SBP), contractile state of the heart, and increase of heart rate (HR). 2) To assess the exercise capacity. The major factor determining the exercise capacity is the ability to increase the cardiac output; the product of stroke volume (SV) and HR. o In normal individuals, cardiac output (Q) typically increases by a factor of four to sixfold from the resting condition to peak exercise. During moderate to high-intensity exercise, the further increase in Q is primarily attributable to an increase in HR, as SV generally reaches a plateau at 50–60% of maximal oxygen uptake.  Hemodynamic Responses Heart Rate (HR): Increases linearly with exercise is intensity due to sympathetic nervous system activation and decreased parasympathetic tone. Stroke Volume (SV): Increases initially with exercise intensity due to increased venous return and contractility. on g it due to the Cardiac Output (CO): Increases significantly is effects combined in of increased HR and SV. s oxygen delivery to working muscles. This ensures adequate x.mn BP increases linearly with Blood Pressure (BP): Systolic exercise intensity due to increased CO and me peripheral a.si i vasoconstriction in non-exercising muscles. Diastolic BP remains relatively stable or may slightly decrease.  IT is as t.ms in exercising muscles Total Peripheral Resistance (TPR): Decreases due to vasodilation to facilitate blood flow and oxygen delivery. This is counteracted by vasoconstriction in non-exercising muscles to maintain systemic BP. a Pulmonary Vascular Resistance (PVR): Decreases due to increased lung volume and recruitment of pulmonary capillaries, facilitating gas exchange. I answer me t Arteriovenous Oxygen Difference (a-vO2 diff): e1fi am Increases due to greater extraction of oxygen by working muscles. This indicates enhanced oxygen utilization at the tissue level. cnet.im i  Abnormal Hemodynamic Responses c ie IEsi.ihi ask isa a summit di a in an n.io F  Monitoring hemodynamic responses during exercise ECG testing provides valuable information about the cardiovascular system's ability to adapt to stress. Abnormal responses may indicate underlying cardiovascular It_IT disease or impaired functional capacity, prompting further investigation or modification of management strategies. Clinical Values  sarin joint i'm im Ind as a enemies on now  Additional Clinical Values im a6 ama.o can provoke at i Evaluation of Arrhythmias: Exercise or worsen 6 certain arrhythmias, aiding in their diagnosis and management. Assessment of Unexplained Symptoms: Helps evaluate patients with unexplained chest pain, shortness of breath, or dizziness. I'm to patients Psychological Benefits: Can provide reassurance with negative results, reducing anxiety related to cardiac health. METABOLIC EQUIVALENTS MET (Metabolic Equivalent Term) The amount of oxygen consumed while sitting at rest, equal to 3.5 mL O2 per kg body weight × min. 1 MET = "Basal" aerobic oxygen consumption to stay alive = 3.5 ml O2 /Kg/min are commonly used to express the workload in various stages of the exercise ECG testing protocols. In the majority of patients with CAD, a workload of 8 METs is often sufficient for evaluation of angina pectoris. Healthy sedentary subjects are seldom able to exercise beyond a workload of 10–11 METs. Physically active individuals may be capable of achieving workloads in excess of 16 METs. When correlating cardiac functional capacity with exercise workload expressed in METs, the following relationships are generally observed: Functional class III patients often become symptomatic at a workload of 3–4 METs. Functional class II patients often are limited by symptoms at workloads of 5–6 METs. Functional class I patients should be capable of achieving workloads in excess of 7–8 METs AGE PREDICTED MAXIMUM HR Age Predicted Max HR= 220 - age in years Targeted HR= 85% of Max Predicted HR. Maximum HR ↓ with age A high degree of variability exists among subjects of identical age (±12 beats per minute [bpm] INDICATIONS g can be used for diagnostic or prognostic purposes, including those with.. Symptoms suggesting myocardial ischemia Acute chest pain in whom acute coronary syndrome (ACS) and myocardial infarction have been excluded Recent ACS treated without coronary angiography Known coronary heart disease (CHD) and change in clinical status Prior coronary revascularization www.msn.w.si. m i or equivocal Abnormal as as findings t.im.ws a.smi on coronary computed tomography angiography Valvular heart disease Certain cardiac arrhythmias  it In CONTRAINDICATIONS  Relative Contraindications we sine Relative contraindications of Exercise ECG Testing are situations where the test may be performed with caution, after careful consideration of the risks and benefits, and with appropriate modifications or precautions. LIMITATIONS TO EXERCISE ECG TESTING Patients who are unable to exercise sufficiently due to leg claudication, arthritis, deconditioning, pulmonary disease, or other conditions. Patients with ECG changes at rest that can interfere with interpretation of the exercise test – ECG abnormalities that interfere with the diagnosis of ischemia include: Ventricular preexcitation (Wolff-Parkinson-White pattern) Ventricular paced rhythm Left bundle branch block Greater than 1 mm ST depression at rest Wolff Parkinson White Syndrome (WPW) presence of a short PR interval (< 120 ms) A wide QRS complex longer than 120 ms with a slurred onset of the QRS waveform, termed a delta wave, in the early part of QRS. Exercise ECG Testing Protocols Various protocols have been developed for exercise ECG stress testing with no single protocol being universally suitable. Use of a particular protocol should include consideration of the objective of the test and patient characteristics. Bruce Protocol one of the most popular protocols utilized in exercise laboratories. The protocol is comprised of seven stages where speed and grade are increased at three-minute intervals. Advantages of being relatively short in duration and extensive validation. may be unsuitable for some cardiac or elderly patients. Modified Bruce Protocol Some patients are unable to begin at the workload of the first stage of Bruce protocol. As such, the Modified Bruce protocol was developed, with the first two stages performed at 1.7mph with a 0 and 5% grade, respectively. This may be helpful in elderly or sedentary patients Naughton Protocol Gradually increases workload between stages and may be a good choice for elderly and deconditioned patients. Methodologies of Exercise ECG Testing  Comparison of types of exercise Treadmill exercise protocols are more flexible than bicycle protocols Bicycle and arm ergometry are generally less expensive, less noisy, more portable, and require less space. The ECG data are cleaner, especially at high workload, with bicycle ergometry because of less upper body motion. Blood pressures are also more easily obtained during bicycle exercise, since the upper body is more stable. Older, more-frail individuals, and those with gait, balance, and orthopedic abnormalities may perform better with bicycle or arm ergometry than on the treadmill. REFERENCES 1.Braunwald’s Heart Disease A Textbook of Cardiovascular Medicine. Volume 1.Ninth Edition. 2. Chareonthaitawee. P., Askew. W.J, (2021) Exercise ECG testing: Performing the test and interpreting the ECG results. UpToDate. Retrieved May 22, 2021 from https://www.uptodate.com 3.Crawford. H. Michael et al. ACC/AHA Guidelines for Ambulatory Electrocardiography: Executive Summary and Recommendations. Originally published 24 Aug 1999https://doi.org/10.1161/01.CIR.100.8.886 Circulation. 1999; 100:886–893