From the Guidelines
A downward deflection of the QRS complex in leads V1 and V2 is typically a normal finding, but it can also be associated with certain cardiac conditions such as bundle branch block or ventricular conduction delays, as defined in the 2019 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1. This finding represents the normal electrical activation pattern of the heart, where the electrical impulse travels from the endocardium to the epicardium and from right to left across the interventricular septum. The negative deflection occurs because the electrical forces are moving away from these right-sided precordial leads. According to the 2019 guideline, a complete right bundle branch block (RBBB) is defined by a QRS duration ≥120 ms, an rsr', rsR, or rSR pattern in leads V1 or V2, and an S wave of greater duration than the R wave or >40 ms in leads I and V6 in adults 1. However, if the QRS complex shows an abnormally deep or wide negative deflection in these leads, it could suggest other conditions such as left ventricular hypertrophy, bundle branch block, or ventricular conduction delays. The interpretation of ECG findings should always be done in the context of the patient's clinical presentation, as isolated ECG findings rarely provide definitive diagnostic information without clinical correlation. It's also worth noting that the 2009 AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram provide similar criteria for diagnosing RBBB, including an rsr, rsR, or rSR pattern in leads V1 or V2, and an S wave of greater duration than the R wave or greater than 40 ms in leads I and V6 in adults 1. However, the 2019 guideline is more recent and provides a more comprehensive overview of cardiac conduction disorders. Therefore, the most recent and highest quality study, the 2019 ACC/AHA/HRS guideline, should be prioritized when interpreting ECG findings, including a downward deflection of the QRS complex in leads V1 and V2 1. Some key points to consider when evaluating a downward deflection of the QRS complex in leads V1 and V2 include:
- The presence of a normal QRS duration and morphology in other leads
- The absence of other ECG abnormalities, such as ST-segment elevation or depression, T-wave inversion, or QT interval prolongation
- The patient's clinical presentation, including symptoms such as chest pain, shortness of breath, or palpitations
- The presence of underlying cardiac conditions, such as coronary artery disease, cardiomyopathy, or valvular heart disease.
From the Research
Downward Deflection of QRS in V1 and V2
- A downward deflection of the QRS complex in leads V1 and V2 can be indicative of several conditions, including Brugada syndrome, idiopathic ventricular arrhythmias, and myocardial infarction 2, 3, 4.
- Brugada syndrome is characterized by a positive terminal deflection and ST segment elevation in the right precordial leads, which can be observed in leads V1 and V2 2.
- Idiopathic ventricular arrhythmias can also present with a downward deflection of the QRS complex in leads V1 and V2, particularly those originating from the left ventricular papillary muscles 5.
- A study found that QS complexes in V1 and V2 without other electrocardiographic abnormalities can have multiple possible causes, including prior myocardial infarction, but this ECG pattern is a sign of prior myocardial infarction in only a minority of cases 4.
- Another study proposed a novel criterion for the differential diagnosis of wide QRS complexes and wide complex tachycardia using the initial activation of QRS on leads V1 and V2, which can aid in distinguishing between premature ventricular contractions and conducted supraventricular impulses with bundle branch block 6.
Clinical Significance
- The clinical significance of a downward deflection of the QRS complex in leads V1 and V2 depends on the underlying condition, and further evaluation and testing may be necessary to determine the cause and appropriate treatment 2, 3, 4, 5, 6.
- In some cases, a downward deflection of the QRS complex in leads V1 and V2 can be a sign of a life-threatening condition, such as Brugada syndrome, and prompt medical attention is necessary 2.