Stress-ekg

In the 1920s, Reindel already did stress tests on himself. The first systematic definition of a stress ECG examination goes back to Rosenkranz and Drews in 1964 (Erdmann 2000).

A stress ECG is a dynamic stress under controlled conditions (Herold 2020) according to the WHO scheme (Erdmann 2000).

Ergometry is the most common and usually the first examination method in the context of suspected coronary heart disease to detect myocardial ischemia. It is used both for diagnosis and for estimating the further prognosis (Kasper 2015).

WHO scheme:

According to the WHO scheme, ergometry involves an input load of 25 W or 50 W. The load is increased by 25 W every 2 minutes. In this way a sufficient load is usually possible for most patients (Erdmann 2000).

BAL-scheme: Since the WHO-scheme for competitive athletes would result in a very long duration of exercise, the Federal Committee for Competitive Sports has developed a separate scheme for this group of patients, the so-called BAL-scheme. This scheme starts with 50 W or 100 W and is increased by 50 W every 3 minutes (Erdmann 2000).

Pathophysiology: The dynamic load during ergometry increases the cardiac output (heart rate x stroke volume = HF x SV = HZV) and additionally induces an increase in oxygen demand.

In the presence of significant coronary heart disease, this triggers ischemia, which is shown in the ECG as an ST change (Herold 2020).

In cases of suspected CHD, an exercise ECG (ergometry) is still part of the initial diagnosis. However, it is becoming less and less important due to the ever-evolving imaging technology. According to the ESC of 2013, sensitivity is reported to be 45%-50%, and specificity is between 85%-90% (Pinger 2019).

It can only be performed under a resuscitation standby (defibrillator), as ergometry carries the following risks:

• 1 to 2 serious adverse events per 10,000 examinations.
• the risk of ventricular fibrillation is 1: 15,000
• the risk of death is 1: 42.000 (Herold 2020)

The stress ECG can be performed differently:

• Symptom-limited: In this case, the stress is increased as long as it is tolerated by the patient.
• Heart rate limited: Suboptimal stress is performed until a certain heart rate limit is reached (220 - life years - 10% to 15% or under therapy with beta-blockers: 167 - 0.7 x life years and also - 10% to 15% ) (Pinger 2019).

Absolute contraindications for a stress ECG are:

• acute myocardial infarction ( ≤ 2 days)
• high-grade main stem stenosis of the left coronary artery (Herold 2020)
• persistent unstable angina pectoris
• Hemodynamically effective arrhythmias that are as yet uncontrolled
• severe symptomatic aortic valve stenosis
• severe heart failure in stage NYHA III and IV (Herold 2020)
• decompensated heart failure
• deep vein thrombosis
• severe pulmonary hypertension (Herold 2020)
• pulmonary infarction
• pulmonary embolism
• acute myocarditis
• acute pericarditis
• active endocarditis
• acute aortic dissection
• significant aneurysm of the aorta or heart (Herold 2020)
• Existing physical inability to adequately and safely perform the test (Pinger 2019).

If there is already an ST-segment depression of ≥ 0.1 mV at rest, a stress ECG should not be performed (Pinger 2019).

Relative contraindicationsare:

• Non-severe main stem stenosis (Herold 2020) or equivalent.
• Moderate to severe valvular stenosis that has an unclear relationship to symptoms
• prolongation of QT time (increased risk of ventricular fibrillation [Herold 2020])
• Uncorrected diseases such as.
  • Anemia
  • Electrolyte disturbances
  • hyperthyroidism
• severe arterial hypertension with values at rest of systolic > 200 mmHg and diastolic > 110 mmHg
• Tachyarrhythmia with uncontrolled ventricular rate
• Atrial fibrillation with uncontrolled ventricular rate
• Bradyarrhythmia (Herold 2020)
• acquired high-grade or complete AV block
• HOCM with a pronounced resting gradient
• Patient's inability to cooperate (e.g., due to mental retardation, etc.) (Pinger 2019).

Absolute discontinuation criteria are:

• - ST- elevation of ≥ 1 mm with the exception of leads with Q- jag (as a sign of a previous old infarct), AVL, V1, and AVR (Pinger 2019)
• ST- decrease of ≥ 0.3 mV (Herold 2020).
• Blood pressure drop > 10 mmHg under increasing stress accompanied by signs of ischemia (Pinger 2019)
• Hypertensive dysregulation with RR- values of systolic > 230 mmHg or diastolic ≥ 115 mmHg.
• Absence of systolic blood pressure rise
• occurrence of polymorphic extrasystoles
• Occurrence of volleys
• Occurrence of a higher-grade AV block
• Occurrence of bundle branch block (Herold 2020)
• - Signs of reduced perfusion such as pallor, cyanosis, etc.
• Occurrence of moderate to severe angina pectoris
• Central venous symptoms such as dizziness, ataxia, presyncope, etc.
• Arrhythmias and/or ventricular tachycardias inconsistent with required cardiac output, such as sustained ventricular tachycardias > 30 sec (Herold 2020)
• ECG or blood pressure monitoring is no longer warranted
• - The patient's wish (Pinger 2019).

Relative discontinuation criteria are:

• Horizontal or descending ST- drop of > 2 mm measured 60 ms - 80 ms after the J- point in a patient with ischemia.
• Blood pressure drop of > 10 mmHg under increasing stress, even without signs of ischemia (Pinger 2019)
• Couplets (Herold 2022)
• increasing angina pectoris
• Fatigue
• shortness of breath
• Sweating
• muscle cramps
• muscle pain
• Arrhythmias that may compromise hemodynamic stability with increasing complexity (does not apply to ventricular tachycardias)
• Occurrence of bundle branch block indistinguishable from ventricular tachycardia
• Increase in blood pressure > 250 / > 115 mmHg (Pinger 2019).

Limited assessment

The stress ECG can only be assessed to a limited extent in the case of:

• existing left or right bundle branch block.
• WPW
• Pacemaker ECG (Herold 2020)
• Treatment with various medications such as:
  • Antidepressants
  • Digitalis
  • Quinidine
  • These medications may cause a decrease in the ST segment. If reasonable, these medications should be discontinued prior to the stress ECG (Herold 2020), otherwise the stress ECG should not be used to diagnose CAD due to insufficient specificity (Pinger 2019).

The test is considered pathological if an ST-segment depression of at least 0.1 mV is measured between 60 ms - 80 ms after the J-point (transition from the QRS complex to the ST-segment).

(Pinger 2019)

The following possible changes during ergometry:

decrease of the ST- distance

• Horizontal or descending reversible ST- decreases in the limb leads of at least 0.1 mV or in the chest wall leads of at least 0.2 mV are typical of myocardial ischemia (Herold 2020)

Less specific are:

• sluggish ascending ST- tract, which 80 ms after the J- point (denotes the point at which the QRS- complex merges into the ST- tract) is still 0.1 mV below the zero line (or 60 ms after the J- point if the heart rate is > 130 / min).

(Stierle 2017)

• Elevation of the ST segment of > 0.1 mV in leads without Q (Herold 2020).

Pathological ST- stretch depression is associated with significant stenosis of at least one coronary artery of > 50%.

In rare cases (5%-11%), ST-segment depression occurs only at rest. It corresponds in diagnostic value to that of depression during exercise.

(Stierle 2017)

Elevation of the ST segment

Significant ST elevations (> 1 mm elevation) are rarely found in the stress ECG. If these occur in leads with pathological Q, they are of no diagnostic significance.

In all other leads, they indicate critical ischemia or coronary spasm. Localization of ischemia is possible based on the distribution pattern in the 12- channel ECG.

(Stierle 2017)

Ventricular extrasystoles (VES).

VES occurring during exercise are not specific for ischemia. If multiple VESs (> 7 / min, couplets or triplets) occur in the first 5 min during the recovery phase, this is associated with a slightly worse long-term prognosis.

(Stierle 2017)

Supraventricular extrasystoles (SVES).

SVES rarely occur during exercise (in about 6%) and are not associated with myocardial ischemia. However, they do indicate an increased risk for future VES .

(Stierle 2017)

Ventricular Tachycardia (VT).

VT are rarely due to transmural ischemia. However, they can occur as part of complications of exercise-induced hypotension and are considered an ischemic response until proven otherwise.

(Stierle 2017)

RR- drop

A drop in blood pressure during exercise indicates an unfavorable prognosis in 3- vascular disease or left main stem stenosis.

An RR- drop > 10 mmHG accompanied by angina, VES, or ischemia signs is an absolute criterion for termination.

(Stierle 2017)

Thigh block

If a patient has prior left bundle branch block (LSB), primary diagnosis of CAD using an exercise ECG is not recommended because ST depression is physiologic in LSB.

In right bundle branch block (RSB), leads V1 to V3 cannot be used. All other leads should be evaluated as usual.

If LSB, RSB, or hemiblock occur during the stress ECG along with angina, it indicates severe septal ischemia.

(Stierle 2017)

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2. Herold G et al (2020) Internal medicine. Herold Publishers 241 - 242
3. Herold G et al (2022) Internal medicine. Herold Publishers 241
4. Kasper D L et al (2015) Harrison's Principles of Internal Medicine. Mc Graw Hill Education 1582 - 1585
5. Kasper D L et al (2015) Harrison's internal medicine. Georg Thieme Publishers 1925 - 1927.
6. Pinger S (2019) Repetitorium cardiology: for clinic, practice, specialist examination. Deutscher Ärzteverlag. 32 - 35
7. Stierle U et al (2014) Clinic guide to cardiology. Elsevier Urban and Fischer 154 - 158