Widely Split P Waves After Pharmacologic Cardioversion in a Patient With Atrial Fibrillation

We report a case of a clinically asymptomatic patient with extreme P-wave separation on the electrocardiogram mimicking atrial tachycardia with atrioventricular block. The accurate examination of the patient, analysis of the electrocardiogram, and echocardiographic findings led to proper diagnosis, management, and treatment. (Level of Difficulty: Intermediate.)

shortness of breath, symptoms related to a new episode of AF (Figure 1A).Physical examination revealed blood pressure of 125/70 mm Hg, heart rate of 70 beats/min, and saturation of 94%.There were no signs of pulmonary edema.The electrocardiogram (ECG) after restoration of sinus rhythm showed widely split P waves.

PAST MEDICAL HISTORY
The patient has a medical history of paroxysmal atrial fibrillation (AF), arterial hypertension, left ventricular diastolic dysfunction, and polymyalgia rheumatica.
She was on therapy with a beta blocker (amiodarone was stopped a few days before), edoxaban, and prednisolone.She underwent pulmonary vein isolation (PVI) for AF 9 years earlier.The patient is known to have a first-degree atrioventricular (AV) block and incomplete right bundle branch block (Figure 1B).

DIFFERENTIAL DIAGNOSIS
Differential diagnoses of split P waves include atrial tachycardia (AT) with AV block.At first glance, the surface ECG (Figure 1C) appears to show AT because there are 2 P waves present for every QRS complex.On further inspection, though, it becomes apparent that P-P 0 timing is different from P 0 -P timing, and thus

LEARNING OBJECTIVES
To be able to make a differential diagnosis between interatrial conduction delay and AT with AV block on the surface ECG.typical AT with AV block to the ventricle can be excluded.The morphology of both P waves was also slightly different.Finally, the presenting rhythm before flecainide (Figure 1A) could also be explained by AT with variable AV conduction.An ECG (Figure 1C) after the restoration of sinus rhythm showed widely split P waves associated with each QRS complex, most distinct in chest leads V3-V4.

INVESTIGATIONS
The distance between the first P-wave to the QRS complex was 400 milliseconds and from the second   Noninvasive assessment of LA fibrosis is challenging.A significant correlation is reported between the lower values of the LA strain and the presence of atrial fibrosis. 6The LA strain in our patient is seriously decreased (Figure 3).AF is associated with increased atrial fibrosis, which can explain the presence of interatrial delay in these individuals. 6erefore, we assumed that in our patient, preexisting atrial fibrosis aggravated the flecainide effect, which is usually much less pronounced.The unique part of our case is that we were able to detect mechanical atrial dyssynchrony with echocardiography (Video 1).
The final decision for the patient was optimal medical therapy, no antiarrhythmic drugs, and a short follow-up.

FOLLOW-UP
After 3 months, the patient was in sinus rhythm with a normal P-wave, with persistence of first-degree AV block, and without any clinical symptoms (Figure 1D).

CONCLUSIONS
The presence of completely split P waves on the ECG is a rare and still unclear phenomenon.

Shumkova et al
Laboratory tests showed elevated troponin and N-terminal pro-B-type natriuretic peptide levels with normal thyroid function.Coronary angiography ruled out coronary artery disease.The patient was hemodynamically stable without any symptoms.

(P 0
) to the QRS complex was 140 milliseconds, yielding an interatrial conduction time (P-P 0 interval) of 210 milliseconds.A transthoracic echocardiography revealed preserved left ventricular ejection fraction and biatrial dilatation with moderate mitral and tricuspid regurgitation.Prolonged activation time between the right atrium (RA) and left atrium (LA) is seen during the examination with a significant difference in the time between the opening of the AV valves (Video 1).

Figure
Figure 2A demonstrates that the opening of the tricuspid valve (depolarization of the RA) coincides with the appearance of the first P-wave on the ECG, and in Figure 2B, the opening of the mitral valve (depolarization of the LA) occurs simultaneously with the second P-wave.Based on the patient's medical history, this was the first episode of AF after the PVI procedure.During these years, she presented with first-degree AV block, with an AV conduction time of 240 milliseconds and incomplete right bundle branch block.MANAGEMENT

FIGURE 3
FIGURE 3 Left Atrial Strain: Significantly Low

J
A C C : C A S E R E P O R T S , V O L . 2 5 , 2 0 2 3 Widely Split P Waves Masquerading as 2:1 Conduction Disorder N O V E M B E R 1 , 2 0 2 3 : 1 0 2 0 3 6 To emphasize the role of echocardiography in this differential diagnosis.