1. Intervals:


-PR Interval should be <1 large box
-QRS should be <3 small boxes
-QT interval should be <1/2 of the distance from 1 R wave to another R wave. If its close, you want to correct based on gender, weight, HR. Generally for males you want <440ms, females <460
-TP segment is isoelectric, so if you want to check segment elevation or depression, check against TP.
2. Heart block
-First degree: PR > 1 large box (i.e. >0.2 seconds)
-Second degree:
--Mobitz 1 (wenkebach): PR interval prolonged until it you drop a QRS
--Mobitz 2: PR interval is the same, QRS randomly drops. Dangerous because it can progress to complete block. Indication for pacemaker.
-Third: complete block, P and QRS separate
3. LBBB: 
-V1- normal R wave, since R side depolarizes normally. S wave is widened, represents L side because electrical activity is moving away from V1 lead.
-V5-V6: widened R wave, because that represent the slow movement of current through L ventricle towards V5/V6 leads.
4. RBBB:
-V1: normal small initial R wave because of the electrical current through the septum (and its facing semi-perpendicular to the V1 lead), then a normal S wave representing normal current through the L side, and then a widened second R wave (R') representing slow movement of current through the R side.
-V5/V6: normal R, widened S?
5. R atrial enlargement: enlarged P wave in lead II, perhaps more current parallel to lead?
L atrial enlargement: squashed P wave in lead II, perhaps more current perpendicular to lead?
6. Ischemia
-T-wave inversions or ST depression (at least 2 small blocks down) in 2+ leads that go together. = ischemia.
-ST elevation: ongoing infarction, STEMI
-Q-waves (>1/3 of the entire amplitude of QRS): infarct, past.
7. Localizing ischemia 
Septal: V1/V2 (LAD)
Anterior: V3/V4 (LAD)
Lateral: V5/V6/I/aVL (circumflex)
Inferior: II/III/aVF (RCA)
8. CT windowing 
-Standard brain window 80/35 (35 HU center, 40 on either side)
-Narrow window 30/30: stroke, hypodense; more contrast
-Wider window 130/50: bleeds, incl isodense subdural
-Soft tissue 400/40: hematoma
-Bone 2000/300: fractures, sinuses, mastoid air cells.

9. CT Contrast

-Contrast ct- to look for tumor/infection

-Stroke: ct to r/o hemorrhagic stroke. IV tPA within 3 hours, IA tPA within 6 hours

-MRI without contrast (DWI) more sensitive for stroke

IV contrast

-GFR > 60: full dose

30-59 : half dose

<30 no contrast unless pros outweight cons.

Default to omipaque (water soluble); more dangerous if aspirated than barium, less dangerous if it goes into your peritoneum

10. Differential dyspnea

Pulm

-Vessels –PE, pulm htn

-Chest wall – obesity, deformity, weakness

-Pleura – effusion, pneumothorax, viral pleurisy

-Airways – asthma, bronchitis/COPD

-Parenchyma – interstitial fibrosis, pneumonia, malignancy

Cards

-Vessels: ischemia

-Valves

-Muscle : chf (sys, dias)

-Electrical (arrhythmia brady)

-Pericardium: effusion