A stress ECG is an electrocardiogram (synonym: stress ergometry) performed under stress – that is, physical activity.The stress is generated by physical work using a treadmill or bicycle ergometer. Depending on the number of watts, the load can be anything from normal walking to fast cycling or jogging. By means of the stress ECG, stress-induced cardiac arrhythmias as well as excitation recovery disorders can be provoked and documented.
Indications (areas of application)
- Clarification of thoracic pain (angina pectoris/”chest tightness”; sudden onset of pain in the cardiac region including vasospastic angina pectoris) in myocardial ischemia (reduced blood flow) in coronary artery disease (coronary artery disease).
- In patients with cardiac risk factors, such as suspected coronary artery disease, arterial hypertension (high blood pressure).
- After myocardial infarction (heart attack) to assess prognosis, physical activity, medication and cardiac rehabilitation.
- After revascularization (revascularization) – restoring blood flow – by interventional techniques or aortocoronary bypass surgery to assess residual ischemia (residual inferior blood flow).
- Acquisition of physical exercise capacity (physical performance capacity).
- Examination of asymptomatic men > 40 years or women > 50 years before physical training.
- In occupations where disease has an impact on public safety (eg, bus drivers, pilots).
- In patients with cardiac arrhythmias, in which the arrhythmias often occur only under stress (eg, ventricular tachycardia in arrhythmogenic right ventricular disease, coronary artery disease)
- Work trials in patients with rate-adaptive pacing systems to set the optimal intervention rate.
- Evidence of adverse proarrhythmic effects-amplification of arrhythmias of antiarrhythmic therapy.
- Measurement of performance capacity (physical endurance) – in high performance or competitive athletes using bicycle or treadmill ergometry.
Absolute contraindications (contraindications)
- Unstable angina – unstable angina is said to occur when symptoms have increased in intensity or duration compared with previous angina attacks
- Acute peri/myo/endocarditis (pericarditis/heart muscle inflammation/pericarditis).
- Acute myocardial infarction (heart attack; within the first two weeks).
- Severe heart failure (cardiac insufficiency; NYHA III, IV).
- Acute aortic dissection (wall bulge of the aorta).
- Aneurysm of the heart or aorta.
- High grade main stem stenosis
- Severe pulmonary hypertension (pulmonary hypertension).
- Respiratory global insufficiency (marked hypoxia/deficiency of oxygen with lowered partial pressure of oxygen (pO2) and a CO2 retention with an increased partial pressure of carbon dioxide (pCO2)).
- Pulmonary embolism
- Manifest heart defects (severe symptomatic aortic stenosis, HOCM).
- More severe anemia (anemia)
- Allgmeinerkrankungen such as fever
- Medication not adjustable cardiac arrhythmias, hypertension.
- Z. n. OP if necessary with surgeons clarify
Relative contraindications
- Arterial hypertension (high blood pressure).
- Tachy- or bradyarrhythmia (occurrence of arrhythmias with pronounced high or low pulse rates).
- AV blockages (conduction disorders from the atrium to the ventricle).
- Known electrolyte disturbances (electrolyte levels/blood salts in the body deviating from normal levels).
The procedure
Through electrocardiography, the electrical activities of all the heart muscle fibers can be derived and displayed as curves in the electrocardiogram (ECG). There is a special stimulation system in the heart in which the electrical excitation is formed, which is then propagated through the conduction system. The excitation is generated in the sinus node, which is located in the right atrium of the heart. The sinus node is also called the pacemaker because it drives the heart at a certain frequency.It is controlled by the sympathetic and parasympathetic nervous systems (vagus nerve), which thus significantly influence the heart rhythm. From the sinus node, the electrical impulse travels via fiber bundles to the AV node (atrioventricular node). This is located at the junction with the ventricles (heart chambers) and regulates the transmission of impulses to the heart chambers. The period of excitation conduction is called the atrioventricular conduction time (AV time). This corresponds to the duration of the PQ time in the ECG. If the sinus node fails, the AV node can take over the function as the primary rhythm generator. The heart rate is then 40-60 beats per minute. If there is a severe delay in the transmission of impulses by the AV node or if it fails, the clinical picture known as AV block occurs. The electrical impulses are conducted with the help of electrodes (suction electrodes; adhesive electrodes). The electrodes (number: 10) are placed on the chest for this purpose. An ECG device amplifies these impulses and either displays them as an ECG curve (electrocardiogram) on a screen or prints them out on a strip of paper. Before starting the exercise, a resting ECG is written and the resting pulse and blood pressure are determined before the exercise. The patient is then exercised on a bicycle ergometer, for example, in a defined manner according to the WHO scheme (ergometer test). The number of watts, i.e. the load, is continuously increased by 25 watts at regular intervals of two minutes. In addition to recording the ECG, the pulse (= heart rate) and blood pressure are measured at the same time in order to obtain further valuable information about the performance of the heart. The minimum heart rate that should be achieved during a seated exercise ECG is calculated as follows: maximum heart rate (Hfmax): [220 minus age in years] per minute.Caveat (note): bradycardia medications (medications that lower heart rate; discontinue sufficiently long beforehand if possible).
Discontinuation criteria
- Angina pectoris (German: Brustenge; heart pain).
- Symptoms: progressive dyspnea (shortness of breath), cyanosis, dizziness, cold sweats, ataxia (impaired movement)
- Lack of increase in frequency
- Blood pressure drop of more than 10 mmHg or lack of systolic blood pressure rise.
- Blood pressure > 240 mmHg systolic; > 115 mmHg diastolic.
- ECG
- Increase in arrhythmias (volleys, ventricular tachycardia (VT), increasing supraventricular extrasystoles (SVES), atrial fibrillation/flutter.
- AV block, new onset left bundle branch block.
- ST elevations > 0, 1mV; horizontal ST depressions > 0.2 mV
- Physical exhaustion
- Reaching the maximum heart rate (= defined load level in watts).
Even in the recovery phase after the end of the load, ECG and blood pressure are still recorded for up to ten minutes regularly about every two minutes. The duration of the examination is, depending on the resilience of the patient, between 15-30 minutes. The stress ECG is then evaluated. The duration of exertion, total power, maximum exertion level, changes in heart rate and blood pressure, as well as heart rhythm and ECG changes are recorded. Furthermore, reasons for any discontinuation are listed, if applicable, and complaints are logged.
Interpretation of measured values
Power
The maximum target power for the male is 3 watts/kg body weight minus 10% for each decade of life beyond age 30. The target power for the female is 2.5 watts/kg body weight minus 8% for each decade of life beyond 30 years of age. ECG
The ECG can be used to make a variety of statements about characteristics and diseases of the heart. It should be noted that the surface ECG only indicates the electrical activity of the myocardium and does not reflect the actual ejection fraction. For information on the morphology of the ECG curve, see Resting ECG. For evidence of coronary artery disease (CAD) on exercise ECG:
- ST segment:
- Newly occurring descending or horizontal ST dips (≥ 0.1 mV, 80 msec after the J-point).
- Ascending ST segment (depression ≥ 0.15 mV, 80 msec after the J point).
- Clinical symptoms of CHD: angina (chest tightness, heart pain) and/or dyspnea (shortness of breath).
Sensitivity (percentage of diseased patients in whom the disease is detected by the use of the procedure, i.e. a positive finding occurs) 50-80% and specificity (probability that actually healthy people who do not have the disease in question are also detected as healthy by the procedure) 60-80% of exercise ECG is significantly higher than resting ECG. ECG changes and their possible interpretations are detailed in the respective clinical picture. Blood pressure
Definition of the threshold values for hypertension (high blood pressure) after stress response.
| Systolic (mmHg) | Diastolic (mmHg) | |
| Stress response according to Franz | ||
| 100 W to 50 years | ≥ 200 | ≥ 100 |
| In-migration per decade over 50 | 10 | 5 |
| Stress response according to Rost and Kindermann (systolic only). | ≥ 145 + 1/3 age + 1/3 watt power. | < 90 |
More hints
- Those who developed blood pressure peaks (systolic value > 210 mmHg (men) and > 190 mmHg (women); as long as the blood pressure peaks occurred in the third minute of a 3-minute exercise level, respectively) despite antihypertensive therapy under ergometer testing or or physical exercise are at risk of developing hypertension and left ventricular hypertrophy (LVH; pathological enlargement of the left ventricle).
Heart Rate
Endurance capacity is a reflection of the functional reserve capacity of the heart. It is characterized by a rapid recovery capacity, as indicated by the pulse response after the end of exercise (recovery pulse). The assessment refers to the decrease in heart rate 1, 3, or 5 minutes after exercise:
| Decrease in heart rate after 5 minutes | Rating |
| < 20 | bad |
| 20 – 30 | Moderate |
| 30 – 35 | sufficient |
| 35 – 45 | good |
| 45 – 50 | very good |
| > 50 | excellent |
Note
- Exercise ECG has a sensitivity of approximately 50% and a specificity of more than 80% in the context of ischemia diagnosis.
- Imaging modalities such as stress echo, stress perfusion MRI, dobutamine stress MRI, myocardial perfusion SPECT, and CT angiography are clearly superior to exercise ECG with a sensitivity of more than 80% without sacrificing specificity.
- The ESC guideline recommends for a pretest probability of coronary artery disease (CAD) of:
- 15-65%: if possible, a modern imaging modality such as stress echo, stress MRI, or myocardial perfusion SPECT should be used; alternatively, exercise ECG; if the pretest probability is 15-50%, CT angiography is also recommended as an alternative.
- 66-85%: diagnostic imaging should always be sought.
- > 85%: invasive coronary angiography (form of X-ray examination in which the coronary arteries (arteries that surround the heart in a wreath shape and supply the heart muscle with blood) are imaged; performed as part of a cardiac catheterization (CCU)).
- Follow-up analysis of the SCOT-Heart study in patients with stable angina:
- An exercise ECG is especially helpful if it is pathological (abnormal)!
- If the findings are normal or inconclusive, further clarification is required!
- The negative predictive value of exercise ECG is 96%, with respect to any obstructive coronary artery disease (CAD) 82%.
