Arrythmias And Ecgs

Front 1

What do ECGs chart? Describe the positive/negative directions leading to upward/downward deflection of ECGs.

Back 1

ECG charts ECM charge; Leads are +

Upwards deflection when - to + towards lead

Front 2

Describe the electrical vectors involved in one cardiac cycle and their correlation to PQRST

Back 2

SA => Atrium => AV/His (P)

Spread down bundle; left faster than right (Q)

Septum => Apex => Base (S)

Endocardium to Epicardium (R)

Repolarize Epicardium to Endocardium (T)

Front 3

Describe the J-point's relation to injury current. What does a baseline voltage above the J-point on lead 1 imply?

Back 3

J-point is the true isoelectric point and occurs immediately after QRS. Injury current describes the relative negative charge that accumulates around ischemic cardiac tissue due to loss of Na/K/ATPase maintenance of charge.

A baseline voltage above the J-point on lead 1 usually results in ST depression. This implies an ischemic right heart border, which results in a constant electric vector towards lead 1.

Front 4

Describe the anatomical relations of V1-V6. What does a V2 STEMI mean?

Back 4

These look at ventricles:

Right ventricle

- V1-2: (4th intercostal, peristernal)

Septum/Apex & LV Anterior Wall

- V3: Between V2 and V4

- V4: septum (5th intercostal, midclavicular)

LV Anterior &Lateral Wall

- V5: (lvl of V4, anterior axillary)

- V6: (lvl of V4, mid-axillary)

Front 5

Describe coronary circulation

Back 5

From Aortic valve:
-RCA nodal branch, right marginal and wraps around to posterior. Gives off posterior interventricular artery before anastomosing with circumflex.

-LCA splits into circumflex and ant. interventricalar/ L. ant. descending artery. This travels towards to apex, wraps around to anastamose with posterior interventricular

Front 6

Describe what affects ECG voltage

Back 6

Voltage increases with hypertrophy. Similarly, loss of conducive mass (e.g. MI scar) reduces. Insulation of heart from leads also reduces (e.g. pleural effusion, barrel chest)

Front 7

Describe ECG waves/interval ranges and what affects them

Back 7

P: 80-120ms

QRS: 60-100

PR: 160-200

QTc: 70bpm <400; 80bpm <380

Describe the rate of conduction. Increases with distance (hypertrophy), blocks or non-fiber conduction (ectopics)

Front 8

Describe the types of conduction blocking

Back 8

SA blockage

AV/Junctional Blockage

-1st: Increased PR interval

-2nd: Type I (wenckebach); Type II

-3rd: Complete

Purkinje Block: RBBB, LBBB

Front 9

Describe electrical alternans phenomenon

Back 9

Alternating high/low voltage qrs

Can occur in cardiac tamponade/effusion where heart physically wobbles on its axis.

Pseudo-alternans is due to partial purkinje block, usually due to tachycardia (incomplete repolarization). Effectively means less heart mass every other beat => reduced voltage

Front 10

Describe ectopic beats and how ECGs can be used to discern their origin

Back 10

A premature contraction not stimulated by sinus rhythm. Tends to resets the cardiac cycle again. Results in pulse deficit due to less filling

-Atrial: Location (e.g. near AV) can shorten PR and invert P-wave.

-Junctional: P/QRS superimposing => distortion

-Ventricular: Wider QRS. Unilateral depolarization can lead to tall QRS. Spaced out depolarization also alters repolarization => T-wave change

Front 11

Causes and results of Long QT syndrome

Back 11

Most commonly caused by medication (Na/K blockers, some antibiotics). Also caused by hypocations and congenital channel problems.

Increases chances of ventricular ectopics, which - given their slow conductive nature - can cause arrythmia, tachycardias and fibrillation.

Front 12

Describe supraventricular tachycardias and the subtypes

Back 12

A form of paroxysmal tachycardia. These are ectopic beats leading to escape rhythms due to re-entrant circuits. Seldom life threatening. They are categorized by origin:

-Atrial: Tend to superimpose on T-wave as it's premature. Depending on location, can invert P

- AV origin: Simultaneous P/QRS wave; sometimes the p-wave can even be absent

Front 13

Mechanism for atrial fibrillations and their difference from flutter

Back 13

Fibrillation relies on discordant, multiple re-entry pathways (circus current). Due to elongated pathways, decreased conduction or decreased refractory. Results in irregular RR.

Flutter is a coordinated flutter (i.e. impulse collectively circles atrium). Consecutive P-waves tend to be visible, with a fraction leading to QRS.

Ventricular fibrillation is the same thing.

Front 14

Cardiac effects of electrolytes

Back 14

These can alter resting membrane potential / affect ion channels. HypoMg, Ca, K for example cause long QT syndrome, probably due to decreasing K membrane permeability. Hyperkalemia in contrast raises resting potential => less Na permeability. Also less K permeability.