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ECG 診斷：

Atrial flutter with 2:1 and 3:1 block

Circulation ECG Challenge Response! Regarding the 56 year old woman with AF and palpitations:

Diagnosis: atrial flutter with 2:1 and 3:1 AV block

There is a regular rhythm at a rate of 130 bpm. There are several longer RR intervals (↔). The QRS complex duration is normal (0.08 sec) and the morphology is normal. The axis is normal between 0° and +90° (positive QRS complex in leads I and aVF). The QT/QTc intervals are normal (280/410 msec). There are P waves seen, primarily in lead V1 (+) and there is a short RP (┌┐) and long PR (└┘) interval. Etiologies for a short RP interval include:
1. sinus tachycardia
2. atrial tachycardia
3. ectopic junctional tachycardia
4. atrial flutter with 2:1 AV conduction
5. typical atrioventricular nodal repentant tachycardia (unusual variant termed slow-slow)
6. atrioventricular reentrant tachycardia
During the longer RR intervals (↔) two sequential P waves can be seen (+, ^). They have a stable PP interval at a rate of 260 bpm. The only atrial arrhythmia that has a regular rate ≥260 bpm is atrial flutter. Therefore there is 2:1 and 3:1 AV block.

ECG Diagnosis: Atrial tachycardia

Circulation ECG Challenge Response! Regarding the 25 year old woman with palpitations:

Diagnosis: Atrial tachycardia

The rhythm is regular, except for one long RR interval. The initial rate is 140 bpm and is followed by several complexes at a rate of 100 bpm. The QRS complex has a normal duration (0.08 sec) and morphology. The axis is normal between 0° and +90° (positive QRS complex in lead I and aVF). The QT/QTc intervals are normal (320/430 msec). There are no P waves before the first 10 QRS complexes and last 6 QRS complexes; there however P waves (+) noted after each of these QRS complexes with a long RP interval (└┘) and short PR interval (┌┐). The P waves are negative in leads II and aVF. This is a long RP tachycardia, There is a P wave before each of the next 4 QRS complexes (i.e. complexes 11-14) (*) with a stable PR interval (0.16 sec). This is a normal sinus rhythm. The etiologies for a long RP tachycardia include a sinus tachycardia (no the cause as the P waves are negative in leads II and aVF), an ectopic junctional tachycardia, atrial tachycardia, atrial flutter with 2:1 AV block or conduction, atypical atrioventricular nodal reentrant tachycardia (i.e. fast-slow), or an atrioventricular reentrant tachycardia. The arrhythmia terminates abruptly without a P wave (↑). This is the way atrial arrhythmias terminate. Therefore this is most likely atrial tachycardia. As there is only one P wave seen this is not atrial flutter. The P wave is different from the sinus P wave and is negative in leads II and aVF) and this is not sinus tachycardia. Arrhythmias generated within or require the AV node terminate with a non conducted P wave.

Diagnosis: Normal sinus rhythm, interpolated junctional premature complexes in a bigeminal pattern.

Circulation ECG Challenge Response! Regarding the 57 year old man with a cough and fever:

Diagnosis: Normal sinus rhythm, interpolated junctional premature complexes in a bigeminal pattern.

There is an irregular rhythm, although there is group beating, with long intervals that are all the same (↔) and short RR intervals that are the same. The average rate is 120 bpm. The short intervals are the result of premature complexes. There are 4 much longer RR interval (↔) and there a distinct P waves at the end of each of these longer intervals (+). The P waves are positive in leads I, II, aVF and V4-V6. Hence these are sinus P waves and they are associated with a stable PR interval (0.16 sec). Complexes 5-6 are two sequential sinus complexes; the rate is 76 bpm. Based on this PP interval it can be seen that there are P waves (*) seen before every other QRS complex and the PP interval is stable (└┘) at a rate of 76 bpm. Therefore there is an underlying sinus rhythm. The QRS morphology of the sinus complexes is normal and there is a normal duration (0.08 sec). The axis is leftward at approximately -30° (positive QRS complex in lead I, negative QRS complex in lead aVF and biphasic in lead II. There are nonspecific ST-T wave abnormalities (^) in leads I, aVL, and V6 (^). The QT/QTc intervals are normal (320/450 msec). The premature QRS complex has the same morphology as the sinus complex but there is no preceding P wave. Therefore these are premature junctional complexes. As every other QRS complex is a premature junctional complex, this is junctional bigeminy. Additionally there is no pause following the premature complex and the PP interval surround the premature complex is the same as the sinus interval. Hence these are interpolated premature junctional complexes in a bigeminal pattern. Also supporting the junctional etiology is that the junctional complexes have a different amplitude compared to the sinus complexes. This is due to the fact that the impulse generated from a junctional focus enters the bundle of His at a different location compared to impulses coming though the AV node. Conduction through the Purkinje system therefore is different.