The short P-wave — Is it really short?

An 82 year-old woman with atrial flutter and fibrillation (AF), currently in persistent AF, has undergone radiofrequency-ablation of cavotricuspid isthmus and electrical cardioversion to restore sinus rhythm. Electrocardiogram (ECG) after the procedure showed an unusual morphology of the P-wave, which was examined more closely. The ECGs are presented in the Figure 1.

Figure 1.

Twelve-lead electrocardiogram tracings; A. Paper speed at 50 mm/s and enhancement ×16, the P-wave duration of 112 ms, PR interval 216 ms, QRS complex duration 104 ms; B. Paper speed at 100 mm/s and enhancement ×32, the P wave duration of 120 ms, PR interval 228 ms, QRS complex duration 102 ms; C. Paper speed at 200 mm/s and enhancement ×64, the P-wave duration of 206 ms, PR interval 229 ms, QRS complex duration 99 ms. The vertical lines mark the beginning and the end of the P wave in each setting. The arrow presents the real end of the P wave.

The complete Bachmann’s bundle block cannot be recognized because no negative P-wave deflection in inferior ECG leads is present, thus we assume a fusion of concomitant activation of the left atrium through the simultaneously activated Bachmann’s bundle and coronary sinus. A more speculative explanation is that the depletion of left atrial cardiomyocytes is leading to a low amplitude of the terminal P wave deflection.

A recent population study of 285,933 individuals assessed the P-wave duration and its clinical importance. In the follow-up the authors observed the development of AF and cases of death were clearly related to a very short P-wave (< 89 ms). The intermediate, long and a very long P-wave also increased the risk of AF and death in comparison to reference duration (90–110 ms).

The standard ECG recording could contribute to such measurement inaccuracies which would be responsible for the category of ‘short P-wave’ and to the conclusions which are having a clinical impact on many patients. In fact, there are interatrial conduction disturbances and prolonged P-wave duration. It should be suspected, especially in the elderly with a history of atrial arrhythmia. To address the issue, we suggest a paper speed of 50 mm/s and a double gain of 0.5 mV/10 mm.