Objectives and diagnostic capabilities
The introduction of functional tests allows the practicing physician to solve several important clinical tasks at once:
- Differential diagnosis: reliable verification or exclusion of the ischemic genesis of cardiac pain.
- Assessment of functional status: in patients with established coronary artery disease, tests help calculate the tolerated workload, the volume of work performed, and determine the body's reserve capacity.
- Prognostic evaluation: the appearance of objective signs of ischemia already at the stages of low physical exertion is a marker of an extremely unfavorable prognosis.
- Additional indications: detection of arrhythmias specifically provoked by activity, as well as monitoring the state of coronary blood flow after myocardial revascularization (coronary artery bypass grafting, angioplasty).
How the cardiovascular system reacts
During a stress test, the specialist continuously evaluates hemodynamic parameters, the ECG pattern, and performs auscultation if necessary.
Physiological norm:
- A predictable increase in heart rate (HR).
- An increase in both systolic and diastolic blood pressure.
- A slight ST-segment depression (strictly less than 1 mm) is acceptable on the ECG, provided that the T waves remain positive.
Signs of pathology (at peak exertion):
- ECG markers: the main criterion for developed ischemia is a horizontal or downsloping ST-segment depression of more than 1 mm. In rare cases, its elevation is recorded.
- Rhythm disturbances: the onset of pronounced arrhythmic episodes as a reaction to stress.
- Auscultatory changes: the appearance of a gallop rhythm indicates left ventricular failure. The onset of a systolic murmur indicates papillary muscle dysfunction developing due to regional ischemia.
Criteria for immediate test termination
The stress test must be stopped immediately if dangerous subjective complaints from the patient or objective instrumental signs of deterioration appear.
Subjective symptoms:
- Typical anginal chest pain.
- Sudden dizziness, severe pallor of the skin.
- Development of a presyncopal state or full syncope.
Objective instrumental data:
- Registration of pronounced ST-segment depression on the monitor.
- The appearance of prognostically dangerous arrhythmias or severe conduction disorders.
- Excessive, physiologically inadequate increase in heart rate.
- Paradoxical drop in systolic BP despite continuing physical exertion. This is a critical sign of a decline in myocardial pumping function.
Safety and complication classification
Any test modification or artificial heart rate stimulation carries a risk of complications, up to and including sudden cardiac death (SCD). Medical personnel must be prepared to provide emergency resuscitation care, and the patient's prior written consent is required.
Potential complications are traditionally divided into two main groups:
- Cardiac: include hemodynamic and ischemic catastrophic events (myocardial infarction, severe arterial hypotension), various rhythm and conduction disorders (sinus, junctional, or ventricular bradyarrhythmias, AV blocks). Fatal arrhythmias causing SCD include asystole and ventricular fibrillation.
- Non-cardiac: mechanical trauma is possible, along with the development of severe generalized weakness (especially typical for deconditioned, sedentary patients) and neurological symptoms (dizziness, syncope).
Briefly: answers to topical questions
What are the absolute and relative contraindications for performing exercise tests in cardiology?
The available materials do not contain a classification of absolute and relative contraindications, but additional restrictions for performing tests in patients with arterial hypertension are highlighted.
Such contraindications include:
- Uncontrolled blood pressure — failure to achieve target BP levels.
- Severe complications — serious complications of hypertension, including cardiac rhythm disorders and pronounced target organ damage.
- Comorbidity — concomitant diseases in the stage of decompensation.
To memorize absolute indications for stopping the test, use the "SAD" rule: Symptoms (anginal pain, pallor, syncope), Arrhythmias (appearance of dangerous rhythm disturbances), and Depression of ST or drop in BP with increasing load.
Class and exam questions
What is considered the main reliable sign of ischemia on the ECG during the test?
The main ECG criterion is a horizontal or downsloping ST-segment depression of more than 1 mm. Pathological elevation is significantly less common in clinical practice.
Why is a drop in systolic BP with increasing physical exertion a warning sign?
A drop in blood pressure in response to increased physical work indicates a sharp decline in the heart's pumping function against the background of acute ischemia. If this sign appears, the test must be stopped immediately.
Is a small shift of the ST segment considered normal during high physical activity?
Yes, a minor ST-segment depression (less than 1 mm) is physiologically permissible, but strictly on the condition that the T waves on the electrocardiogram remain positive.
What else to study on this topic
- Detailed analysis of vector ECG and topical diagnosis of ischemic zones during stress tests.
- Differential diagnosis of the causes of a gallop rhythm occurring at peak physical exertion.
- Pathophysiological mechanism of systolic murmur development (papillary muscle dysfunction) during transient ischemia.
- Prognostic formulas and scales for assessing functional reserves in patients with severe CAD.
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