Pulsus alternans has been discussed under the arterial pulse previously. The alternation of the strong and the weaker pulse can be detected while taking blood pressure. Corresponding to the alternating strength of the palpated pulse, one also can note alternating blood pressure levels. During deflation of the inflated cuff to record the systolic pressure, one will notice that initially the Korotkoff sounds begin to be heard only with every other stronger beat rather than with every beat as would occur in the normal. With continued deflation of the cuff, there will be a doubling of the rate of the Korotkoff sounds because both the strong and the weak beats will come through. In addition, one may also note an alternating intensity of the Korotkoff sounds. In general, pulsus alternans is associated with severe left ventricular dysfunction and low cardiac output. Pulsus alternans is usually precipitated by an extrasystole. The phenomenon can be shown to develop following a premature beat in almost all patients. However, in those with normal left ventricular function, it lasts only for two beats and is not noticeable clinically but may be shown by the measurement of the systolic time intervals (mentioned previously under the arterial pulse). In very severe left ventricular dysfunction, the pulsus alternans effect produced by a premature beat may persist for a long time (for several minutes). There may be instability ofthe calcium flux in the myocytes ofthe diseased heart, which may account for the alternating strengths of the contraction of the myocardium in the patients with myocardial disease (49).
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