Pacemakers are not difficult to work out.

BACK TO INDEX

The nomenclature of what type of pacemaker it is, and how it is sensing and pacing can be challenging, however, most of that information will be on the patient's pacemaker card.

​Here are 3 paced ECG's.

ATRIAL PACED RTHYTHM
​The pacemaker spikes appear before the P waves.

VENTRICULAR PACED RHYTHM
Spikes appear before the QRS complex. It produces a LBBB morphology, due to right ventricular pacing. There is discordance between the T waves and the QRS compelxes.

​DUAL CHAMBER PACING
​There are pacing spikes before both the p waves and the QRS complexes.

Problems with Pacemakers

The main issues with pacemakers are:

• Failure to conduct
• Failure to Capture
• Failure to Sense

​Naming Pacemakers

1st letter – chamber/s where stimulation(pacing) occurs

• A=atrium,
• V = ventricle,
• D = dual chamber

2nd letter refers to chamber where sensing occurs

3rd letter refers to how the pacemaker responds to a sensed event

• I= the output pulse is inhibited
• T- the output pulse s triggered. Usually chambers paced and sensed and the response to sensing

An Example

Ventricular Paced.   Inhibited Impulse if the Ventricles contract
V       V       I                                 
Ventricular Sensing

​Here is what a classic VVI pacemaker would look like.

​Here is a DVI pacemaker

D- Dual Chamber ie paces both atrium and ventricle
V- Only senses the Ventricle
​I- Inhibited by ventricular activity

AV Sequential Pacing
This is sometimes called AV sequential pacing where both the atria and ventricles are paced.
It is used in patients who have lost their atrial kick. It's purpose is to improve ventricular filling. It can increase cardiac output by up to 50%

PACED ECG TROUBLESHOOTING- TRY THESE EXAMPLES

START WITH A 4 STEP APPROACH TO TROUBLESHOOT.

1. What is the rate?
2. is there a P wave or QRS after each pacing spike?
3. Are pacing spikes seen throughout the ECG?
4. Are there pacing spikes where they shouldn't be?

CASE 1: A 60 YO MALE WITHA VVI PACEMAKER, PLACED 3 MONTHS AGO PRESENTS WITH FATIGUE, MALAISE AND WEAKNESS. WHAT DOES THE ECG SHOW? IS THE PACEMAKER FUNCTIONING PROPERLY?

answer

​This is an entity called pacemaker syndrome.

CASE 2: A 76 YO MALE WITH A HISTORY OF ATRIAL FIBRILLATION AND AN AAI PACEMAKER PRESENTS WITH PALPITATIONS. HERE IS HIS ECG.
WHAT DOES AAI MEAN?
IS THERE SOMETHING WRONG WITH THE PACEMAKER?

answer

AAI means that

• ATRIUM is paced
• Atrium senses
• Inhibited

​This is undersensing