12/12/2023 0 Comments Ekg pulseless electrical activity![]() ![]() On the ECG, it is observed as SR with an alteration in the R-R interval >0.12 seconds between different R waves. ![]() This difference may lead to a small beat by beat variation, which is felt clinically as an irregular pulse. Inspiration can inhibit vagal tone increasing the heart rate, whereas expiration can increase vagal tone reducing heart rate. The SAN can be influenced by several external factors including the parasympathetic nervous system via the vagus nerve, and by respiration through reflexes originating in the lungs. If the R-R interval differs across beats we can say the rhythm is irregular. If the R-R interval is constant, we can assume the rhythm is regular. heart block, extra beats, abnormal ventricular activity).Īs part of rhythm assessment, it is important to determine whether the ECG trace is regular or irregular.Īssessment of whether a rhythm is regular or irregular refers to the distance between adjacent QRS complexes. When using the term SR, we should comment on the presence of any abnormalities (e.g. However, it is technically correct to only use NSR when all the above defining features apply. In clinical practice, the terms SR and NSR are often used interchangeably. Normal AV conduction: for each p wave there is a corresponding QRS complex in a 1:1 ratio.Normal depolarisation: initiated in the SAN.The other common phrase is ‘normal sinus rhythm’ (NSR), which is a more complete term. The term ‘sinus rhythm’ (SR) refers to depolarisation that is initiated in the SAN. ![]() The normal passage of electrical activity from the SAN to the atrioventricular node (AVN) is seen as P waves with normal morphology (positive deflection in lead II, negative deflection in lead aVR). The wave of electrical activity then depolarises the rest of the heart. Under normal circumstances, the sinoatrial node (SAN) initiates electrical activity because it undergoes spontaneous depolarisation first at a rate of 60-100 bpm. In other words, the part of the heart that is initiating electrical activity, which then spreads throughout the conduction system. The rhythm refers to the area of the heart that is controlling electrical activity. On an ECG, rhythm refers to the part of the heart that is controlling the initiation of electrical activity. The length of the ECG rhythm strip is usually 10 seconds making this an easy method. Alternatively, you can multiple the number of QRS complexes within 50 large squares (equivalent to 10 seconds) by 6. It is a quick and easy way to estimate the rate from the ECG. This method can be used for regular and irregular rhythms. For example, if 8 QRS complexes appear within 30 large squares the corresponding rate is 80 bpm. Multiply this number by 10 to give the estimated rate. Multiplication methodĬount the number of QRS complexes that occur within 30 large squares (equivalent to 6 seconds). the distance between two adjacent R waves is constant). This method is used when the rhythm is regular (i.e. For example, if there are 4 large squares between two adjacent R waves, the corresponding rate is 75 bpm. Look at two adjacent QRS complexes and count the number of large squares between the two R waves. There are two ways of calculating the rate: division method and multiplication method. Under normal circumstances, we simply determine the ventricular rate, which will reflect the atrial rate. how frequently the ventricles are contracting). how frequently the atria are contracting) and the ventricular rate (i.e. When looking at the ECG, we can determine both the atrial rate (i.e. Rate on the ECG can be one of three broad categories: Rate is defined as the number of times the heart beats per minute. ![]()
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