Overview.
Sinus pre-systole is also known as refractory pre-systole in the sinus node. Sinus excitation folds back in the sinoatrial node 1 to 2 times, forming sinus pre-systole. Sinus pre-systole has no obvious pathologic significance, but sinus pre-systole can induce sinus node refractory tachycardia (mostly paroxysmal).
Etiology
The etiology may be related to autonomic dysfunction, fever, metabolism, and medications.
Symptoms
There are no obvious clinical symptoms, and they are usually detected by an electrocardiogram during physical examination.
Examination
Electrocardiogram.
Diagnosis
Diagnosis can be made by combining medical history and ECG findings.
Differential diagnosis
1. Sinus arrhythmia
(1) In sinus arrhythmia, changes in the cardiac cycle occur gradually, whereas in sinus pre-systole, the cardiac cycle is abruptly shortened.
(2) Sinus arrhythmia is closely related to the respiratory cycle. The cardiac cycle is gradually lengthened or shortened with respiration, and the frequency is accelerated during inhalation and slowed down during exhalation. Sinus pre-systole has nothing to do with breathing.
2. Atrial pre-systole
The P-wave pattern of atrial pre-systole is different from that of sinus rhythm. In addition, the former compensation interval is also an incomplete compensation interval. However, this compensatory interval is still significantly longer than one sinus cardiac cycle. Although the P wave of sinus pre-systole and sinus P wave can be very similar, its compensation interval is still significantly longer than a sinus cardiac cycle. The P wave of sinus pre-systole is identical to the sinus P wave and has an isoperiodic compensatory interval.
3. Identification of sinus pre-systolic dysthymia and 3:2 sinus block
When sinus atrial conduction is 3:2 block and sinus pre-systolic dysthymia, both of them show paired P-QRS-T, and the length of the P-P interval alternates, and the main points of differentiation are as follows: ① The long P-P interval in 3:2 sinus atrial block is twice as long as the short P-P interval, whereas the long P-P interval in sinus pre-systolic dysthymia is not twice as long as the short P-P interval. (ii) In 3:2 sinus block with Wen’s phenomenon, the long P-P interval is less than twice the normal P-P interval, and it is difficult to distinguish it from sinus pre-systolic dystonic rhythm. If normal sinus rhythm can be recorded, and if the P-P interval of sinus rhythm is equal to the long P-P interval in the paired sinus pre-systolic dysthymia, then it can be diagnosed as sinus pre-systolic dysthymia; if it is equal to the short P-P interval in the sinus pre-systolic dysthymia, then it can be diagnosed as a Wen’s type of 3:2 sinus block.
Treatment
The cause of sinus pre-systole may be related to autonomic dysregulation, fever, metabolism, drugs, etc. Treatment should be directed at the primary cause. No specific treatment is usually required.
Prevention
Maintain optimism and emotional stability; live and work regularly, do not overwork; quit smoking and alcohol, reduce the triggering factors of this disease; dietary control, less fat, sweet, thick and greasy food; active physical exercise, weight control.