What is the pulse rhythm? Sinus arrhythmia is when there is variation of rate with breathing. It accelerates a little on inspiration and slows a little on expiration. This can be quite marked in children and adolescents but is uncommon over the age of 30. It can persist a little longer in the physically fit. The pulse slows on inspiration in pulsus paradoxus and it can occur with pericardial effusion, constrictive pericarditis and severe pneumothorax, especially tension pneumothorax, severe asthma and severe chronic obstructive pulmonary disease (COPD).[1] In normal circumstances, the systolic blood pressure often falls slightly, by less than 10 mm Hg on inspiration, but in pulsus paradoxus it falls by more than this. This fall can be used to assess the severity of cardiac tamponade.[2] Irregularity is more difficult to discern if the rate is fast. Note if it is regularly irregular of irregularly irregular: Variable heart block or premature ventricular excitation will cause either an extra beat or a missed one. Premature ventricular contraction may cause a missed beat because the ventricle has not had time to fill adequately and so the stroke volume is low. The beat following a missed beat, whether due to premature excitation or failure of the ventricle to beat, may be rather stronger than the others, as the ventricle has filled more in the longer diastole. This irregularity will follow a regular pattern. A much more random irregularity is a feature of AF. If the rate is fast in AF, it may be difficult to note if the irregularity is random or even if there is irregularity at all. It may be helpful to measure the rate at both the cardiac apex and the wrist and in AF there is usually a deficit at the radial pulse. This is usually done with two people timing simultaneously but it can be done alone, not timing but merely noting if the rates differ. The rate in AF and the rarer atrial flutter depends upon the degree of A-V block but it can be very fast. It has been suggested that a way to distinguish between causes of irregularity is to get the patient to exercise to increase the pulse rate. In premature ventricular excitation it will reduce or disappear. In AF it will increase the irregularity or at least not reduce it. Currently, most clinicians would use the ECG for a more reliable means of distinction. What is the character of the pulse? Finally, note the character of the pulse. This incorporates an assessment of the pulse volume (the movement imparted to the finger by the pulse) and what has been described as the form of the pulse wave. The pulse character must be interpreted in the light of pulse rate. Cardiac output is the product of stroke volume and heart rate. Thus, a slow pulse may be associated with a high stroke volume and, as there is a long time between each ejection, the pulse pressure (the difference between systolic and diastolic pressure) will be high. In shock, the pulse will be fast but weak. This might be from hypovolaemia or cardiogenic. In congestive heart failure one of the first features is tachycardia. A hyperdynamic circulation occurs in emotion, heat, exercise, anxiety, pregnancy, fever, anaemia and thyrotoxicosis. The pulse rate is raised but the pulse is full and bounding. Cardiac output is high and peripheral resistance is low. Disease of the aortic valve will affect the nature of the pulse wave. In aortic stenosis, the wave is slow to rise and the pattern of the arterial pressure is rather flat - the slow rising pulse. In aortic regurgitation, the stroke volume is high because a significant amount of blood sinks back into the ventricle and has to be pumped again. Furthermore, the incompetent valve will let the arterial pressure fall markedly in diastole. Hence, a bounding, dynamic pulse collapses to give a very wide pulse pressure. This is called a collapsing or water hammer pulse. The water hammer is a piece of Victorian engineering that is rarely seen these days. The collapse of the pulse pressure can be felt with even greater effect if the patients hand is raised over his head so that the radial artery is palpated at a level rather above the heart. Severe aortic regurgitation, classical of syphilitic aortitis, can cause the head to jerk with each pulse (de Mussets sign). In mild aortic stenosis with reflux, the pulse detected may have two peaks as well as being slow rising. This is the so called bisferiens pulse. The next step
Posted on: Sun, 23 Mar 2014 18:08:56 +0000
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