What is the significance of an S-T segment (electrocardiogram segment representing ventricular repolarization) frontal axis deviation of -60 degrees, -36 degrees, -24 degrees, 1 degree, and -36 degrees?

From the Guidelines

The ECG findings show a frontal plane axis deviation with S-T axis measurements of -60 degrees, -36 degrees, -24 degrees, 1 degree, and -36 degrees, which is consistent with left axis deviation, typically defined as an axis more negative than -30 degrees, as stated in the study by 1. This pattern can be caused by several conditions including left ventricular hypertrophy, left anterior fascicular block, inferior myocardial infarction, or can be a normal variant in some individuals. The varying measurements across different leads suggest that the electrical activation of the heart is predominantly directed superiorly and to the left, rather than the normal inferior and rightward direction. This altered electrical pathway may reflect structural or conduction abnormalities in the heart that should be correlated with clinical symptoms and other diagnostic findings before determining clinical significance. Further cardiac evaluation including a complete 12-lead ECG, cardiac history, physical examination, and possibly additional cardiac testing such as echocardiography is warranted. Some key points to consider in the interpretation of these findings include:

• The distinction between primary and secondary repolarization abnormalities, as discussed in the study by 1
• The importance of considering the spatial orientation of the ST-segment vector in both the frontal and transverse planes, as recommended in the study by 1
• The potential for left axis deviation to be associated with various cardiac conditions, including left ventricular hypertrophy and left anterior fascicular block, as noted in the study by 1
• The need to correlate ECG findings with clinical symptoms and other diagnostic findings to determine clinical significance, as emphasized in the study by 1.

From the Research

S-T Front Axis Analysis

The provided information regarding the S-T front axis readings (-60 deg, -36 deg, -24 deg, 1 deg, -36 deg) does not directly correlate with the studies presented, which primarily focus on left axis deviation (LAD) and its implications in patients with left bundle branch block (LBBB).

Left Axis Deviation Studies

• The study by 2 discusses left axis deviation as a common ECG abnormality that may indicate underlying structural heart disease.
• 3 investigates the pattern of mechanical asynchrony in patients with LBBB and LAD, suggesting that these patients may have poor response to resynchronization therapy (CRT).
• 4 finds that LAD in patients with LBBB is a marker of myocardial disease associated with poor response to CRT.
• 5 examines the relationship between electrocardiographic characteristics of LBBB and echocardiographic findings, concluding that LBBB is associated with elevated prevalence of cardiac structural disease.
• 6 suggests that left-axis deviation in patients with nonischemic heart failure and LBBB is a purely electrical phenomenon, related to differences in cardiac electrophysiology rather than structural factors.

Key Findings

• LAD is associated with underlying structural heart disease and poor response to CRT in patients with LBBB 2, 3, 4.
• LBBB is linked to a high prevalence of cardiac structural disease, making it challenging to apply common ECG criteria for diagnosis 5.
• LAD in LBBB patients appears to be an electrical phenomenon, related to delayed activation of the basal anterolateral region 6.

Implications

• The presence of LAD in patients with LBBB may indicate a higher risk of myocardial disease and poor response to CRT.
• Further research is needed to fully understand the mechanisms underlying LAD in LBBB patients and its implications for treatment and prognosis.