Transcript Related Guidelines

Tips for Right Heart Catheterization in Patients With PAH

Ryan J. Tedford, MD · Medical University of South Carolina

Disclosures

April 15, 2021

Key Takeaways:

  • Tips for right heart catheterization in patients with pulmonary artery hypertension (PAH) include:

    • Study the patient and the catheterization protocol

    • Accurately measure the wedge pressure

    • Thermodilution is preferable to indirect Fick measurement of cardiac output

    • Vasodilator testing should be conducted in selected patients (ie, those being considered for transplant and those with idiopathic or drug-associated PAH)

    • Considering only rest hemodynamics may be inadequate

This transcript has been edited for clarity.   

Very excited to be with you today and share the Tedford top five tips for right heart catheterization. I would ask that you remember that the reports that you generate are considered absolute truth and so make sure these reports reflect the gold standard and not fool's gold. 

So the number one tip is study before you start. What do I mean by that? I always tell my trainees, my fellows, to study the patient characteristics and profile, know what you're going to find before you begin the right heart catheterization. What is the pretest probability of pulmonary hypertension? What is the pretest probability of left heart disease? If you find something that you didn't expect, make sure you know why that is and account for it. Is the right atrial pressure going to be high? And did you confirm that when you place your venous sheath? 

What else do I mean by study before you start? Well, study the system. Have you properly zeroed the system? Is it at the appropriate level, which is the midchest? Is the system calibrated? What is your baseline EKG starts? All mundane tasks, yet very important for accurate assessment. And finally, checking a saturation of the superior vena cava will help you exclude an intracardiac left-to-right shunt. 

The number two tip, and probably the most important, is getting the wedge pressure right. There's three key aspects to this. The first is to understand how to assess this in respect to the respiratory cycle. In most individuals, an end expiration intrathoracic pressure is going to be closest to 0, and will have the least impact on your numbers. And so for most individuals measured in at end expiration is what we want to do. 

In patients with severe parenchymal lung disease or in patients with severe obesity, intrathoracic pressure may not be closest to 0 at end expiration. And for those individuals, we may want to average over the respiratory cycle. Secondly, we have to understand how to measure with respect to the cardiac cycle. 

At end diastole, pressure in our pulmonary veins, our left atrium, and our left ventricle should all be equal. And so, if we want to estimate left ventricular end-diastolic pressure, we're going to want to measure at end diastole. That typically is done by averaging the peak and the trough of the A wave. However, in the presence of large V waves from mitral regurgitation or due to a stiff left atrium, the wedge pressure averaged over the cardiac cycle, or mean wedge, will actually be higher than your end-diastolic wedge. And this is really what is felt by the pulmonary circulation. So if we're trying to calculate a pulmonary vascular resistance, this type of measure may be more appropriate. 

And finally, we want to confirm that we have a complete wedge occlusion whenever we find an elevated wedge pressure. And that's not always possible to tell just from the waveform or with fluoroscopy, so we want to measure a wedge saturation. As we pull back blood from the distal tip of the catheter with the balloon inflated, that blood will begin to turn bright red if we have a complete occlusion, and the saturation of that blood should approximate that of the systemic circulation. 

The number three tip. Thermodilution is preferred over an indirect Fick. Why is that? Well, indirect Fick, we estimate oxygen consumption. And these estimates are very poor, particularly in pulmonary hypertension and heart failure. If you can measure oxygen consumption directly with a direct Fick, certainly that's the gold standard. But in the absence of that, and even in situations of severe tricuspid regurgitation or low cardiac output, thermodilution is the preferred methodology to estimate cardiac output. 

Number four. Vasodilator testing. There's really two scenarios we want to consider this. First in patients who are undergoing an evaluation for heart transplantation with an elevated PVR. With nitroprusside, if we can lower that PVR to less than 2.5 units while maintaining a systolic blood pressure greater than 85, these individuals may be considered safe for transplant from a pulmonary vascular standpoint. 

The second group is those with idiopathic or drug-associated pulmonary arterial hypertension. In those individuals, we give them nitric oxide to determine if they may respond to monotherapy with calcium channel blockers, and it may also give us information about prognosis. We need to lower their mean pulmonary artery pressure by at least 10 mm Hg to an absolute value of less than 40 while maintaining or increasing the cardiac output. 

And the final and number five tip for the right heart catheterization is, considering only resting hemodynamics may be inadequate. Well, we can imagine patients may be NPO for a long period of time, or on oral diuretics, or have been diuresed, in fact, before the right heart catheterization. And a normal wedge pressure may not reflect true left heart pathology. In situations where we have a high pretest probability of left heart disease, but a wedge pressure that's in the borderline range, we want to consider giving those patients a fluid challenge, typically that's 500 mL of saline over 5 minutes. And if the wedge pressure goes to more than 18, this is consistent with left heart disease. 

Exercise can also be considered at expert centers to differentiate group 1 from group 2 pulmonary hypertension. May also be helpful in determining if someone has exercise-induced HFpEF or pulmonary hypertension, preload insufficiency, or may also be helpful in measures of ventricular reserve. 

So there you have it, the Tedford top five tips for performing the right-heart catheterization.

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