Role of ECG in the diagnosis of heart failure
According to the modern multidisciplinary algorithm combining Russian, European, and American guidelines, evaluating the electrocardiogram is an obligatory first step when chronic heart failure (CHF) is suspected in patients with a non-acute onset of the disease.
Along with indications of a past myocardial infarction and the presence of arrhythmias, it is specifically voltage changes of the QRS complex that prompt the physician to suspect structural pathology. The detection of these signs on an ECG, especially in combination with a characteristic medical history (coronary artery disease, arterial hypertension, use of cardiotoxic drugs) and physical examination findings (lung rales, displacement of the apical impulse, jugular venous distension), serves as a direct indication to proceed to the next diagnostic stage: laboratory determination of natriuretic peptide levels (BNP or NT-proBNP).
Voltage criteria as a marker of arterial hypertension
When assessing the severity of arterial hypertension, voltage criteria play a key role in establishing the stage of the disease. The presence of ECG signs of left ventricular hypertrophy is classified as asymptomatic target organ damage.
The detection of such changes automatically classifies the patient into stage II arterial hypertension (provided there are no associated clinical conditions such as myocardial infarction, stroke, or severe chronic kidney disease). This, in turn, directly influences the determination of the cardiovascular risk category, which can range from low to extreme.
Main voltage indices
To objectify signs of left ventricular hypertrophy, specific calculated parameters are used. Reliable ECG signs of asymptomatic myocardial damage include:
- Sokolow-Lyon index: calculated as the sum of the S wave amplitude in lead V₁ and the R wave amplitude in leads V₅ or V₆. A result exceeding 35 mm is considered diagnostically significant.
- R wave amplitude in lead aVL: an isolated increase in the height of this wave to 11 mm or more.
- Cornell voltage index: calculated by summing the amplitudes of the S wave in lead V₃ and the R wave in lead aVL. This parameter has gender differences: a value greater than 28 mm for men and greater than 20 mm for women is considered pathological.
- Cornell product: a comprehensive parameter, a value of which exceeding 2440 mm × ms also indicates hypertrophy.
Further verification of structural changes
If the voltage signs on the ECG are complemented by an elevation in biomarkers (threshold values: BNP > 35 pg/ml or NT-proBNP > 125 pg/ml), the patient must undergo echocardiography.
It is ultrasound examination that allows for the final confirmation of hypertrophy via the assessment of left ventricular mass index and relative wall thickness. In addition, echocardiography helps determine the CHF phenotype (with reduced, mildly reduced, or preserved ejection fraction) and assess diastolic function parameters, including the E/e' ratio and pulmonary artery systolic pressure.
To memorize the essence of the Sokolow-Lyon index, use the "right-left" rule: take the deep S wave from the right precordial lead (V1) and sum it with the tall R from the left ones (V5-V6).
Class and exam questions
What is the clinical significance of QRS voltage changes?
They indicate probable left ventricular hypertrophy, which is a sign of asymptomatic target organ damage in arterial hypertension and an important step in the CHF detection algorithm.
How is the Sokolow-Lyon index calculated?
It is necessary to sum the amplitude of the S wave in lead V₁ and the amplitude of the R wave in lead V₅ (or V₆). If the sum is greater than 35 mm, the index is positive.
How does the Cornell voltage index differ from others?
The main feature of the Cornell voltage index is that it accounts for the patient's sex: the threshold value for men is >28 mm, and for women it is >20 mm.
What should be done if ECG voltage signs of pathology are found?
Further evaluation is required: according to clinical guidelines, when CHF is suspected, it is necessary to assess the level of natriuretic peptides and perform echocardiography to visualize structural changes.
What else to study on this topic
- Echocardiographic criteria for left ventricular hypertrophy and left ventricular mass index calculation
- Algorithm for using natriuretic peptides (BNP and NT-proBNP) in the diagnosis of CHF
- Classification of chronic heart failure by ejection fraction phenotypes
- Parameters for assessing diastolic function and left ventricular filling pressure
- Associated clinical conditions in stage III arterial hypertension
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