Lead impedance change threshold and cause

Low lead impedance 

< 200 ohms

Indicate insulation breach

Usually inner insulation in a bipolar coaxial lead

High lead impedance 

> 2000 ohms

Indicate open circuit

Lead fracture or loose set screw

Hysteresis

In single chamber devices, for ventricular pacing, hysteresis allows a longer cycle length after a sensed event than after a paced beat. 

It helps maintain intrinsic rhythm and preserves battery. 

In summary: Hysteresis is a programmable feature that allows the pacemaker to begin ventricular pacing only if the spontaneous rate falls below a set rate (eg, 50 bpm); then pacing continues at the programmed base rate (60 bpm) unless intrinsic ventricular activity is sensed.

Low voltage criteria on ECG mnemonic

Entire amplitude of the QRS (R + S wave) must be < 5mm in all limb leads or < 10mm in all precordial leads. How do I remember this? Mnemonic!​

- IkaN (Nakeya Dewaswala)

EKG quiz #1

What does this EKG show? 

Answer will be posted soon.

-IkaN

Read EKGs with me #1

Answer below:

Normal P wave ECG notes and mnemonic

Here is the video:

 

Mnemonic:

Notes:
Sinus P waves
Axis: 0 and +75 degrees
Upright: Leads I, II, V5, V6
Inverted: aVR
Duration: <120ms or 3 small squares
Amplitude:
Limb leads: < 2.5 mm (0.25mV)
Precordial leads: < 1.5 mm (0.15mV)

-IkaN

Determining pacemaker type from EKG (RV pacing vs biventricular pacing)

 Hello, cardiowesomites!

Today we are going to learn how to determine pacemaker type from EKG (RV pacing vs biventricular pacing)

Notes:

ECG axis mnemonic (short version)

Video here:

 

Notes below:

Determining axis of EKG (isoelectric method) practice tracings

How to determine axis of EKG (number, isoelectric method) with mnemonic

Coronary artery dominance and EKG changes

Hello, hello!

Coronary arterial dominance is defined by the vessel which gives rise to the posterior descending artery (PDA).