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The Art and Science of Cardiac Physical Examination (With Heart Sounds, Jugular and Precordial Pulsations)by Narasimhan Ranganathan, Vahe Sivaciyan, Franklin B Saksena
This is a recording from a patient with pulmonary hypertension. The top of the head of the patient is towards the observer's left side. Simultaneous recording of the heart sounds shows a soft S1 and a sharp S2 which is heard well. There is also some inspiratory noise due to the breath sounds. The movement of the jugulars transmitted between the two heads of the sternomastoid are visible just above the clavicle. The jugulars show a single downward movement which occurs at the time of the S2. Since there is some transmission delay to the neck from the right atrium, the descent that occurs with the S2, is systolic and the descent must be the x'. The wave that precedes the single x' descent must be the a wave since the rhythm is regular. The rise of the a wave is also prominent. Since the normal a wave rise is not easily seen, this must be an abnormally prominent a wave. The prominent a wave will indicate decreased right ventricular diastolic compliance. The preserved x' descent will suggest a good descent of the base and therefore good right ventricular systolic function. Prominent a wave is not indicative of pulmonary hypertension, it only means a strong right atrial contraction evoked by the decreased right ventricular diastolic compliance. If the patient has chronic pulmonary hypertension, it will mean an earlier compensated stage. Note that the a wave has a short duration and looks like a "flicker". An experienced clinician will be able to spot this as a prominent a wave merely from the fact that it has a short duration. However it must be remembered that this is not a normal a wave. Occasionally one may come across similar prominent a waves in patients with complete atrio-ventricular (A-V) block In complete A-V block, the atria beat on their own driven by sinus depolarizations and the P waves are not conducted to the ventricles. The ventricles are usually driven by an independent pacemaker which may arise from the A-V junction, or the His-Purkinje system depending on the site of the block. If the patient has an implanted electronic permanent ventricular pacemaker, the ventricular rhythm may be caused by the ventricular pacing. The atrio-ventricular dissociation may be easily seen in the ECG of such patients. Since the atrial contractions are dissociated from those of the ventricles, occasionally merely by chance there could be simultaneous contraction of the atria and the ventricles. When this occurs, the right atrial contraction will occur against a closed tricuspid valve causing a sudden rise in pressure. This will cause a retrograde flow into the superior vana cava and the jugulars. This will cause a rise of the pressure in the jugulars which will be prominent. These prominent a waves are called "Cannon waves". They will be somewhat irregular since they occur merely by chance of the simultaneous contractions of the atria and the ventricles in the presence of A-V dissociation. They may be seen whenever the ventricular rhythm is dissociated from that of the atria.
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