Friday, 9 February 2007

JVP and the ECG

I have been unable to update my blog these last few days as I have been trying to get the new Microsoft Windows Vista to work properly. Having finally succeeded I have been able to update my blog today.

I want to mention something about the Jugular Venous Pulse (JVP) or Distension as the termed is coined elsewhere.

This physical sign is often missed or not even appreciated and through my daily teaching, the junior doctors are now looking for the JVP, and in some cases, it has proven a great diagnostic sign especially with the added help of an ECG (shin-densu).

The JVP is an estimate of the pressure of the venous circulation. It can be raised by many processes but particularly heart failure and atrial fibrillation.

The JVP should only be read with the patient at an incline of 45 degrees and not flat. Hence, you need to sit your patients up, and if they have severe cardiac or respiratory disease, they should be sat up already!

The JVP is measured vertically from the manubriosternal joint (sternal angle) to the top of the JVP wave in centimetres with the head turned to the left and with the physician examining from the traditional right side of the patient. A normal JVP <4cm.

A JVP should be seen as the superficial vein becomes distended over the sternocleidomastoid muscle area. It has a double pulse for every arterial (carotid) pulse. On sitting the patient vertically, unless the problem is very severe, the JVP should disappear. Also, on pressing the liver, the JVP should be seen to rise (Hepatojugular reflex-- I almost never do this as it can be painful and restrict breathing). I also occlude the jugular vein from below upwards thereby allowing me to differentiate whether the raised pressure is truly from the heart or whether it is simply due to filling from the cranial venous circulation.

The JVP has two waves, the first due to blood regurgitating during atrial contraction as it empties into the ventricle and the second as the atrium refills with blood before the ventricle relaxes and the tricuspid valve still remains closed. These are termed as 'a' and 'v' waves respectively.

Hence, the JVP can be predominantly raised with the 'a' wave or the 'v' wave but for the beginner, just seeing if the JVP is generally raised is the important thing.

JVP should be assessed in all patients and it should give a diagnostic clue in conditions such as CHF, large pulmonary embolism, atrial fibrillation, valvular disease, COPD and other chronic respiratory diseases.

A clue as to the cause of the raised JVP can be sometimes seen on the ECG.

For example, today I saw an elderly lady with COPD. Before seeing her I reviewed her ECG which showed peak / tall 'p' waves consistent with the term p pulmonale and hence, right atrial enlargement. Her arterial blood gas revealed a respiratory alkalosis and profound hypoxaemia of 55mmHg. Examination of her JVP revealed large venous waves (the rapid upstroke and rapid down stroke of the venous blood consistent with Tricuspid Regurgitation). She had no obvious right ventricular heave and no murmur as it is likely she has complete TR. She had no peripheral oedema.

The history of smoking, the profound hypoxaemia, ECG changes of the 'p' wave led me to conclude that she had developed Type 1 Respiratory Failure and chronic pulmonary vascular vasoconstriction had caused RA enlargement and TR. This would be consistent with Cor Pulmonale.

Sometimes the ECG will show RV strain (ST depression and T wave inversion) in the RV leads e.g. V1, V2, V3, aVR and with the presence of p pulmonale, hypoxaemia one should also consider pulmonary embolism although other diagnoses such as pulmonic stenosis, mitral stenosis, primary pulmonary hypertension, cardiomyopathy should also be considered amongst others.

Finally, examples of predominant 'a' wave elevations in the JVP include: pulmonary hypertension, pulmonary stenosis.

Large 'a' (Cannon) waves are seen in complete heart block, atrial flutter, single ventricle pacing, ventricular arrhythmias/ectopics.

Absent 'a' waves in atrial fibrillation (no proper atrial contractions!)

Large systolic 'v' waves are seen in Tricuspid Regurgitation.

JVP can be raised for other reasons such as fluid overload, cardiac tamponade, SVC obstruction, constrictive pericarditis.

Good hunting for the JVP!!!