심전도 (EKG, ECG) 읽는 흐름
위급한 질환을 우선 감별한다. : Arrhythmia(rate, rhythm) & Infarction, ischemia (ST segment, T wave)
<Rate & Rhythm>
# Rate (작은 1칸 0.04sec, 큰 1칸 0.2sec)
# Rhythm : R-R 간격 규칙적/ 불규칙적?
# QRS 두께 : narrow / wide (>0.12sec)
# P wave (lead 2에서 +, aVR에서 -), P다음QRS
# PR 간격 연장? - heart block
<ST segment>
# 12 전극 중 어디라도 ST elevation ? 보통 1mm상승 / V2, V3 에서는 2mm상승 기준
# ST elevation 감별질환
: STEMI / Benign early repolarization / pericarditis / vasospasm / pulmonary embolism / LV aneurysm / LV hypertrophy / LBBB
# ST depression (2개 연속 lead에서 0.5mm 하강)
: 평평한 ST depression(ischemia 가능성) / upslopping ST depression & V1~V3에서 peak T wave(proximal LAD occlusion)
# ST depression 감별질환
: NSTEMI / Posterior MI / LBBB / LVH w/ strain / reciprocal change / digoxin toxicity
<J wave>
감별질환 : benign early repolarization / hypothermia / hypercalcemia / Brugada syndrome
<T wave>
# T wave inversion : LVH strain / ICP 상승 / Pulmonary Embolism / BBB / ischemia ("오직 aVL에서 T wave inversion 보이면 inferior MI 의심!)
# Hyperacute T wave(tall, broad, asymmetric) : vasospasm / early STEMI
# biphasic T wave : ischemia(Wellens-A 특히 V2, V3 lead) / hyperkalemia
# flat T wave : ischemia / hypokalemia
# peaked T wave(tall, narrow) : hyperkalemia / hypermagnesemia / ischemia(De-Winters T wave, V2, V3 lead, proximal LAD)
<QRS wave>
# wide (>0.12sec) QRS : BBB / hyperkalemia / V-tach / W.P.W / paced rhythm / medications(TCA)
# LBBB, RBBB : V1, V2 / V5, V6
# pathological Q wave(>0.04sec or >2mm in depth or >25% of QRS) : MI(old or new) / PE / LBBB / LVH
# low voltage QRS : pericardial effusion(HR상승, 호흡곤란) / obesity / COPD / heart failure / infitrated disease
<QT interval>
long QT (>460ms in female, >450ms in male : 대략 R-R 간격의 절반 이상) : Torsade de Pointes(TdP) 위험 / medication 감별 / 전해질 문제(hypo-kalemia, magnesemia, calcemia) / ischemia
<P wave>
Rt/Lt atrial enlargement (lead 2, V1 참고)
<Axis>
left deviation : LBBB / LVH / inferior MI / hyperkalemia
right deviation : RBBB / RVH / anterior MI / V-tach