EKG Heart Rhythms Cheat Sheet - Free Printable

It looks like you've uploaded an image related to artificial cardiac pacemakers, specifically focusing on pacemaker rhythms and malfunctions. However, the image appears to be partially cut off or incomplete — particularly in the "Pacemaker Malfunctions" table, where only one malfunction ("Failure to pace") is visible, and the reasoning column is truncated.

Let’s analyze what we can see and then explain the likely intended content and how to interpret it.

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🔍 Image Analysis

#### 1. ECG Strip with Pacemaker Spikes
- The ECG shows a rhythm with:
- Atrial pacemaker spikes: These are small vertical lines (arrows) preceding the P waves.
- Ventricular pacemaker spikes: These precede the QRS complexes.
- This suggests dual-chamber pacing (both atrial and ventricular).
- The presence of both atrial and ventricular spikes indicates that the pacemaker is actively pacing both chambers.

#### 2. Pacemaker Malfunctions Table
Only one row is visible:
| Malfunction | Reason |
|------------------------|----------------------------|
| Failure to pace | Pacemaker spikes |

This is incomplete. Likely, the full sentence should read:

> Failure to pace: Pacemaker spikes are present, but no corresponding P wave (atrial) or QRS complex (ventricular) follows.

This is a classic definition of failure to capture — meaning the pacemaker fires (spike), but the heart does not respond.

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✔ Understanding Pacemaker Malfunctions

Here are common pacemaker malfunctions and their interpretations:

| Malfunction | Description | ECG Finding |
|--------------------------|-----------------------------------------------------------------------------|-------------|
| Failure to pace | Pacemaker fails to deliver an impulse when needed. | No spike at expected time |
| Failure to capture | Impulse delivered (spike seen), but no myocardial response (no P or QRS). | Spike present, but no P wave or QRS after it |
| Pacemaker oversensing| Pacemaker detects non-physiological signals (e.g., myopotentials) and inhibits pacing. | Absence of pacing spikes when expected |
| Pacemaker undersensing| Pacemaker fails to detect native cardiac activity → unnecessary pacing. | Pacing occurs despite intrinsic beats |

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🧠 Key Concept: "Spikes" vs. "Capture"

- Pacemaker spike = electrical signal from the device.
- Capture = whether the heart muscle responds to that signal.
- If spike is present but no P wave or QRS, → failure to capture.
- If spike is absent when expected → failure to pace.

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🔎 Interpretation of Your Image

From the ECG:
- Atrial and ventricular spikes are present.
- Each spike is followed by a P wave and QRS complex → this indicates successful capture.
- So, this ECG shows normal pacemaker function, not malfunction.

But the table seems to be listing malfunctions — possibly for educational purposes.

The incomplete line under "Failure to pace" likely meant to say:
> Failure to pace: No pacemaker spike is seen when expected (i.e., the device doesn’t fire).

But currently, it says:
> "Pacemaker spikes" — which is confusing unless it's referring to the presence of spikes as evidence of pacing.

So, probably the full phrase was supposed to be:
> Failure to pace: Absence of pacemaker spikes when expected.

Or:
> Failure to capture: Presence of pacemaker spikes without corresponding P wave or QRS.

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✔ Final Explanation

The ECG shown demonstrates normal dual-chamber pacing:
- Atrial spikes → P waves
- Ventricular spikes → QRS complexes
→ This means the pacemaker is pacing and capturing appropriately.

The table is likely meant to teach about common pacemaker malfunctions, such as:
- Failure to pace → no spike when expected
- Failure to capture → spike present, but no P/QRS
- Oversensing → inappropriate inhibition of pacing
- Undersensing → pacing over native rhythm

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🛠️ Suggested Correction to Table

| Malfunction | Reason |
|-------------------------|--------|
| Failure to pace | No pacemaker spike when expected |
| Failure to capture | Pacemaker spike present, but no P wave or QRS complex |
| Oversensing | Pacemaker senses noise and suppresses pacing |
| Undersensing | Pacemaker fails to detect native beats → unnecessary pacing |

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If you can provide more context or clarify the exact question (e.g., “What is wrong with this rhythm?” or “Identify the malfunction”), I can give a more targeted answer.

But based on the image:
> ✔ No malfunction is present — the pacemaker is working correctly.