**5. Diagnosis of PH**

The existence of sophisticated monitoring in this particular group of patients is deemed necessary because early diagnosis and prompt institution of therapy for acute PH is required in order to prevent right ventricular failure.

Diagnosis is aided by awareness of existing preoperative risk factors, such as valvular pathology or intracardiac shunts that are associated with PH. The development of acute PH will result in clinical signs of relatively rapid onset relating to the development of tricuspid regurgitation: prominent central venous atrioventricular pulsatile pressure waveforms, right-sided heart failure and a holosystolic murmur at the lower border of the sternum that increases in intensity during inspiration.

Pulmonary artery pressure catheterization and transesophageal echocardiography (TOE) constitute a valid monitoring tool for early detection of acute PH.

Pulmonary artery pressure catheterization will demonstrate elevated right atrial pressure, right ventricular end-diastolic pressure and pulmonary artery pressure with normal or low pulmonary wedge pressures. In the case of right ventricular dysfunction without pulmonary vasoconstriction, the pulmonary artery pressure may also be normal. Hemodynamic parameters calculated and derived by thermodilution will reflect elevated PVR and a reduction in right ventricular stroke work index and right ventricular stroke work index / central venous pressure relationship and a reduction in cardiac output or right ventricular ejection fraction.

TOE is an invaluable tool in the diagnosis of PH and right ventricular dysfunction, demonstrating both right ventricular volume and pressure overload. The two- dimension mode provides a subjective view of the increased ratio of right ventricle-to- left ventricle chamber size, paradoxical septal bulging, and deterioration in right ventricular function as seen on five-chamber and 4-chamber long axis views (Figure 1).

Color flow mapping will often reveal pulmonary and tricuspid regurgitation. The use of continuous wave Doppler across the regurgitant tricuspid valve allows quantification of the

Fig. 1. Severe tricuspid regurgitation and enlargement of the right ventricle caused by severe pulmonary hypertension

pressure gradient across the valve and thereby an estimation of the pulmonary artery pressure.

Also TOE has been proved to be a useful tool in the continuous assessment of the results of the applied therapeutic strategy.
