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A sinus rhythm is any cardiac rhythm in which depolarisation of the cardiac muscle begins at the sinus node. [1] It is necessary, but not sufficient, for normal electrical activity within the heart. [2] On the electrocardiogram (ECG), a sinus rhythm is characterised by the presence of P waves that are normal in morphology. [2]
Sinus arrhythmia is a commonly encountered variation of normal sinus rhythm. Sinus arrhythmia characteristically presents with an irregular rate in which the variation in the R-R interval is more than 0.12 seconds (120 milliseconds). Additionally, P waves are typically mono-form and in a pattern consistent with atrial activation originating ...
Sinus bradycardia is commonly seen in normal healthy persons and athletes in the absence of pathophysiological diseases or conditions. [1] Different factors or etiologies could lead to the dysfunction of the sinus node, causing a malformation or prolongation of the impulse. In terms of pathophysiological diseases, sinus rhythm may be caused by:
Sinus tachycardia is a sinus rhythm of the heart, with an increased rate of electrical discharge from the sinoatrial node, resulting in a tachycardia, a heart rate that is higher than the upper limit of normal (90-100 beats per minute for adult humans). [1] The normal resting heart rate is 60–90 bpm in an average adult. [2]
Schematic representation of a normal sinus rhythm EKG wave. In electrocardiography, the PR interval is the period, measured in milliseconds, that extends from the beginning of the P wave (the onset of atrial depolarization) until the beginning of the QRS complex (the onset of ventricular depolarization); it is normally between 120 and 200 ms in duration.
Normal sinus rhythm and ectopic beats - premature ventricular contractions (PVC) and premature atrial contractions (PAC) shown on an EKG. PVCs may be found incidentally on cardiac tests such as a 12-lead electrocardiogram (ECG/EKG) performed for another reason. In those with symptoms suggestive of premature ventricular complexes, the ECG/EKG is ...
This is known as an escape rhythm. Since this accessory pacemaker also activates independently of the impulse generated at the SA node, two independent rhythms can be noted on the electrocardiogram (ECG). The P waves with a regular P-to-P interval (in other words, a sinus rhythm) represent the first rhythm.
Non-respiratory causes of sinus arrhythmia include sinus pause, sinus arrest, and sinoatrial exit block. Sinus pause and arrest involve slowing or arresting of automatic impulse generation from the sinus node. This can lead to asystole or cardiac arrest if ventricular escape rhythms do not create backup sources of cardiac action potentials. [2]