Multifocal/Chaotic Atrial Tachycardia With Variable Degree Of Atrioventricular Block, with IRBBB and LVH
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Patient: Woman, 69 y/o with no significant medical history. Presented in the ER with grave sepsis due to unknown focus of infection. Rectal temperature is 40.5°C, BP 170/100, pulse irregular at ca. 150 bpm, SAT 93 % w/O2 3 l/min, RF >50/min, peripher cyanosis, lip cyanosis, marmorated skin over the abdomen and thorax, serum glucosis 8.7. Arterial blood gas analysis showed a minor electrolyte imbalance and a respiratory alcalosis.
ECG interpretation: Multifocal / Chaotic Atrial Tachycardia with Variable Degree of AV Block, incomplete RBBB and Left Ventricular Hypertrophy
ECG description:
- Supraventricular Tachycardia / Narrow Complex Tachycardia
- Atrial ectopic rhythm with highly irregular rate
- Incomplete Right Bundle Branch Block (QRS 120ms)
- Varying P wave morphology and axis. Three or more morphologically distinct P’ waves in the same lead.
- Variable AV Block. P:QRS ratio ranges from 1:1 to 2:1. Several P’ waves buried in QRS complexes.
- Probable Left Ventricular Hypertrophy from Sokolow’s Criteria (RV5 + SV2 >35mm)
Note that there is a:
- Highly varying PP interval, which is due to a varying atrial rate. Mean A-rate is around 135 bpm
- Highly varying RR interval, which is due to a varying ventricular rate. Mean V-rate is around 150 bpm
- Highly varying PR interval, which is due to varying ectopic atrial foci.
- Isoelectric baseline between every ectopic P’ wave.
- No obvious dominant atrial pacemaker, ruling out sinus rhythm with multiple PACs.
Further observations:
- Cardiac axis pointing downwards at approx 90°
- Probable Left Ventricular Hypertrophy according to Sokolow-Lyon Index
- T wave inversion in leads V1-V3
Measured intervals, counting from the first (leftmost) P wave:
- PP (millimetres): 18, 22, 24, 19, 26, 12, 28, 18.5, 17.5, 22, 18
- PR (milliseconds): 80, 100, 80, 65, 100, 60, 70, 115, 120, 115, 80, 65
- RR (millimetres): 19. 21.5, 23.5, 20, 24, 18, 28, 19, 19.5, 19, 18
- All intervals are irregularly irregular.
Multifocal Atrial Tachycardia (MAT)
Term: MAT is also known as chaotic atrial tachycardia, and describes rapid firing of several ectopic atrial foci at a rate faster than 100 bpm.
Occurrence: MAT is often associated with COPD or CHF , but can also occur in the presence of hypokalemia, hypomagnesemia, hypoxia, acute myocardial infarction and mitral stenosis.The condition usually occurs in seriously ill patients, mostly elderly people.
Mechanism: Characterized by P waves of varying morphology, assuming that distinct P waves originate from ectopic atrial foci. The ectopic P waves may be called P’ (P Prime). Due to different automaticity foci, both P wave morphology and axis will vary. The PR interval will also vary, depending on the proximity of each atrial focus to the AV node and the prematurity of each ectopic impulse. Some P waves may be nonconducted, and some may be aberrantly conducted if they get conducted into the ventricles while they are still partially refractory. MAT is often preceded or followed by frequent PACs, sinus tachycardia, AF, A-flutter, ectopic AT or PAT. Compared to WAP (Wandering Atrial Pacemaker), the ecg findings and rhythm characteristics are the same, but in MAT the atrial rate is higher.
ECG characteristics: 1) Three or more morphologically distinct P waves in the same lead. 2) The absence of one dominant atrial pacemaker, in disctinction to sinus rhythm with multiple premature atrial complexes. 3) An isoelectric baseline. 4) Varying PP, PR and RR intervals. Ventricular rate is usually 100 to 150 bpm.
Ladder diagram for lead V1 (click to view larger)
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Ladder diagram description: The ladder diagram shows ectopic atrial foci firing at varying rate and with varying proximity to the AV Node, resulting in varying PR intervals and varying ventricular rate (RR intervals).
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