ECG Interpretation and Cardiac Conditions Overview

ECG Interpretation and Cardiac Conditions
Overview



Duration from Q wave to T wave.

QT Interval



Bazett's Formula QTc = QT / √RR interval.

Prolonged QTc QTc > 450 ms indicates risk.

, Torsades de Pointes, arrhythmia
risk with QTc > 500 ms.
TdP




Normal QT Rule Normal QT is less than half RR

interval. QTi Measurement Leads Use leads II, V5, V6 for

accuracy.

U Wave Measurement Measure to end of U wave if merged.

Right Coronary Artery Supplies right ventricle and inferior wall.
(RCA)

Supplies SA node in 45%, AV
RCA Functions node in 90%.




PDA Dominance 85-90% right dominant, 10-15% left dominant.

Left Circumflex (LCX) Supplies left ventricle and lateral wall.

LAD Functions Supplies anterior and septal walls.

ST elevation in II, III, aVF.

Inferior MI Leads



Posterior MI Leads ST elevation in V7-V9 confirms posterior MI.

Ventricular Aneurysm Occurs with large myocardial damage post-MI.

ST Elevation Duration ST elevation > 2 weeks indicates aneurysm.

Right Ventricular MI Inferior STEMI with III > II.

Horizontal ST depression in V1-V3 suggests posterior
Posterior MI Clues MI.

Reciprocal Changes Changes in V1-V3 indicate posterior

MI. Lateral MI Leads ST elevation in I, aVL, V5-V6.

Septal MI Leads ST elevation in V1-V2 indicates septal MI.