Ask the Clinical Instructor: Why does the physician sometimes use 2 catheters to evaluate a valve, and why sometimes only 1?

Why does the physician sometimes use 2 catheters to evaluate a valve, and why sometimes only 1? – Anonymous RCIS Review participant For a more detailed explanation of valve interrogations, please refer to articles written in April (https://tinyurl.com/CLDApril08), May (https://tinyurl.com/CLDMay08) and June (https://tinyurl.com/CLDJune08) of 2008. This article will give a brief answer to the question, and our three 2008 articles can give you more details on this subject. One of the theorems of hemodynamics is that to know the status of a valve, you must know the pressures above and below the valve. We generally do this with the aortic valve and the mitral valve. Aortic Valve When analyzing the aortic valve, we need to know the pressures on each side of the valve. Of course, this would be the aorta (AO) and the left ventricle (LV). We are probably familiar with the “pullback” across the valve after a ventriculogram (Figure 1). In that process we get a “quick look” at the valve by seeing if there is any gradient of systolic pressures from the LV to the AO. This method has an advantage because it is easy and quick, without the need of any special equipment or set up. The disadvantage is that you only get to see a view of the gradient at the moment of the pullback. Another way to get these measurements is through a dual-lumen pigtail catheter (Figure 2). With this catheter, simultaneous readings from the LV and AO are obtained (Figure 3). The advantage of this method is that a continuous view of the systolic reading from each chamber can be read as long as needed in order to obtain a more accurate reading. The disadvantage is the cost of the extra catheter, and the extra set up needed to use it (two transducers). Another method, less frequently employed, is to obtain a simultaneous reading from the sheath in the femoral artery while the pigtail is in the LV (Figure 4). I don’t believe this is the most accurate process available. Peripheral amplification may have a slight influence on this reading. Also, because of the delay of the waveform making it to the transducer, you would notice that the upstrokes of the LV and the AO don’t exactly match. You would have to phase shift (move the AO pressure tracing) to line up correctly with the LV waveform to get an accurate mean valve gradient. Refer to the documentation for your recording system for more information. Of course, either of these methods depends upon being able to cross a wire and catheter across the valve. In severely compromised valves, this can occasionally not be possible. The use of echocardiography can give a definite answer when valve readings in the cath lab cannot be accomplished. Mitral Valve The chambers on each side of the mitral valve are the left atrium (LA) and LV. Assessing the LA usually requires a different process. Transeptal Procedure The transeptal procedure requires accessing the venous side, and utilizing special equipment, puncturing the atrial septum from the right atrium (RA) and placing a catheter directly through this puncture into the LA (Figure 5). This gives us the ability to measure the LA mean pressure. In most cardiac cath labs, this procedure is generally not used. In facilities that perform electrophysiology (EP) procedures, or where mitral valvuloplasty is performed or atrial septal defects are repaired, this procedure is commonplace. Use of Pulmonary Capillary Wedge Pressure When a pulmonary artery catheter (PAC) is ‘wedged’ into the pulmonary artery capillary, we have accomplished an indirect way to monitor the LA. Essentially, the wedged pressure creates a fluid-filled chamber from the pulmonary capillary wedge (PCW) location to the LA. The PCW can reflect the LA mean (Figure 6). Of course, this assumes normal respiratory status and no disease of the pulmonary beds. When analyzing the gradient, you must account for the delay in the pressures making it from the tip of the PA catheter to our transducer. You will need to phase shift the PCW pressure waveform to the left until the v wave is bisected by the LV downstroke. The computer will calculate the gradient for you at that point. The LA mean pressure SHOULD equal the left ventricular end-diastolic pressure (LVEDP). If there is a difference, then a mitral valve issue should be suspected, assuming pulmonary pathologies have been ruled out. Regardless of which LA measuring method is used, 2 catheters will be needed: either the transeptal catheter and the LV catheter, or the PAC catheter and the LV catheter. Again, obtaining the measurement on each side of the valve is necessary to obtain measurements to evaluate the valve integrity. Email your question to Todd at tginapp@rcisreview.com

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