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What is water-hammer pulse ?

Bounding pulse is commonly seen in hyperkinetic circulatory states, here the pulse volume is high due to highpulse pressure with increased blood flow.
What is water-hammer pulse (or high volume collapsing pulse)?
This pulse is characterised by :
  • High pulse volume 
  • Sharp rise.
  • Ill-sustained
  • Sharp fall.
High volume pulse gives the water-hammer character when the pulse pressure is at least more than  60 mm of Hg. A collapsing pulse usually occurs when there is rapid run-off of blood from the aorta or the arterial system. Carotid artery is used for detecting collapsing nature of pulse
The striking features of collapsing pulse are: 
  • Abrupt upstroke, ill sustained peak and  abrupt downstroke and collapsing feel under the palpating hand
  • Thrust produced by the abrupt upstroke of the collapsing  pulse will resemble the thrust produced by the tilting of the water hammer toy and the abrupt downstroke of the pulse produces collapsing feel.
How will you demonstrate the water-hammer pulse ?
  • First you should palpate the wrist in such a way that your webs fall on the radial artery and rest of the palm lies over the ulnar artery of the patient Now you should e xamine the volume of the pulse for few seconds. 
  • Elevate the whole upper limb suddenly above the  patients shoulder ( you may give a support in the elbow to prevent its flexion) mean while trv to recognise any changes in the volume of the pulse. In water-hammer pulse, the  pulse volume increases from the basal level (i.e. volume at the beginning of the examination) after elevation of patients upper limb.
  • For examination of the pulse in this manner  one should stand within the ‘angle’ formed between the patients body and the said upper extremity. The right sided pulse should be examined by the right hand with the examiner standing on the right side of patient , and vice-versa for the left. You can observe the increase in pulse volume sharp rise and the sharp fall.
Why the name water-hammer pulse is given?

This pulse is so termed after a toy called water-hammer’. This is a peculiar toy with a glass cylinder that is half filled with water and half with vacuum (two ends being closed). If the toy is suddenly placed upside down, the column of water will strike the other end of the cylinder with a blowing sound. This is why this pulse is termed  waterhammer pulse where the pulse strikes the fingers like the thud of a hammer.
What is most important the cause of water-hammer pulse?
It is aortic regurgitation
Why this type of pulse is seen in Aortic regurgitation?
Waterhammer pulse is seen in AR due to the following reasons
High systolic pressure occur due to
  • In AR, as the left ventricular stroke volume is high systolic pressure is also high and it is responsible for sharp rise' in the pulse.
The collapsing nature is due to low diastolic pressure which is seen due to 
  • Diastolic leak back into the left ventricle from aorta.
  • There is rapid run-off to the periphery as a result of decreased systemic vascular resistance, the barorcceptors in the aortic arch is stimulated by increased cardiac output and result is reflex vasodilatation of the peripheral vessels into which the blood flows rapidly.
Why do you elevate the arm for eliciting the collapsing pulse?
  • Due to the effect of gravity, there is fall of blood column with resulting in vasodilatation and thus, it helps to reduce the diastolic pressure more. Hence  the pulse pressure widens,
  • It may be so that while we elevate the limb the artery palpated becomes more in line with that of aorta after elevation of the arm.So it allows direct systolic ejection and diastolic backward flow resulting in collapsing pulse.
What are the other parts to be examined in water hammer pulse?
  • You should count the rate (bradycardia in complete heart block: tachycardia in thyrotoxicosis).
  • See the condition of the vessel wall (for atherosclerosis).
  • See the facies for exophthalmos or examine for tremor to rule out thyrotoxicosis).
  • You should record the surface temperature (pyrexia).
  • Examine for anaemia (severe anaemia).
  • Examine for jaundice to rule out cirrhosis with hepato-cellular failure.
  • Examine the chest for emphysema (chronic cor pulmonale).
  • Always auscultate the aortic and neoaortic area for an earlv diastolic murmur of AR.
  • Search for peripheral signs of AR such as , for capillary pulsation, digital pulsation, carotid dance, pistol shot sound which are associated features of water-hammer pulse.