Ask the Clinical Instructor

Todd is the Cardiology Manager for Memorial Hermann Southeast in Houston, Texas. He also teaches an online RCIS Review course for Spokane Community College, in Spokane, Washington, and regularly presents with RCIS Review Courses. This month, I want to address a question concerning a couple of common “bad” waveforms that we see in the cath lab: ventricularization and damping. A great deal of discussion can occur about the how’s and why’s, and what to do about it. The most important thing is that BOTH ARE BAD! They need immediate identification and remedy to prevent bad things from happening. While a damped waveform and a ventricularized waveform are dramatically different, each has the same impact on coronary flow. Damping (Figure 1) occurs when there is a mismatch between the catheter and the ostium of the vessel. It can also be seen when the tip of the catheter is against the aortic or coronary vessel wall. In cases where the catheter cannulates the ostium and damping is seen, it’s indicative of one of two things. Either the catheter is too large for the ostium, or the tip of the catheter has passed through the ostium and is now slightly against the vessel wall. This is more commonly seen in right coronary artery (RCA) cannulation where there can be tortuosity closer to the ostium. This waveform is also seen after inadvertent cannulation of the conus branch. Damping is evident by a decreasing of the systolic pressure that will generally become a lower and lower pressure. If this damping is allowed to continue in the RCA, the occlusion of the flow will have an effect on the atrioventricular (AV) node O2 supply, as well as the right ventricular outflow tract (RVOT) supply. Since the RVOT is one of the more highly sensitive areas of the heart (as electrophysiology staff may agree), ventricular ectopy/fibrillation can occur. General damping can lead to ventricular fibrillation if allowed to continue. Staff should be able to identify this waveform and have a standard “code word” to use to notify the physician. Sometimes the physicians can be busy with the task at hand, and not always have their eyes on the monitor. Catheter engagement is one of many times that all staff should have eyes on the monitor. Many facilities state words like “pressure” or “damped” or “monitor.” Something to notify the physician but not alarm the patient is prudent. I commonly get the question, “What do I do if the physician doesn’t want me to say anything?” My answer is, would you rather be griped at for saying something, or griped at for NOT saying something while the patient is being defibrillated? Side note: Should you see a damped pressure during peripheral angiography/intervention, it is not the same thing, nor of concern. We are only concerned when it occludes coronary blood flow. Ventricularization (Figure 2) is a slight decrease in systolic pressures, but a large decrease in diastolic pressures. At a first glance, the waveform looks like a left ventricular or ‘LV’ waveform. However, the diastolic pressure is well above the traditional 0-10 that we would see in an LV end diastolic pressure (LVEDP). Ventricularization is most commonly seen when the catheter tip passes through a tight lesion on a left main. While this is a common example, damping and ventricularization can be seen interchangeably in any setting. Wes Todd, BS, RCIS, Director, Cardiac Self Assessment (www.westodd.com), used a great explanation when I was first learning these waveforms. Ventricularization is the equivalent of a backyard garden hose stretched out to wash your car in the driveway. When you turn on the hose, but have the sprayer in “off” mode, the hose fills up with water, but is stopped from running out the end of the hose. If a car drives over the hose while you are holding the sprayer, you feel the sudden increase in pressure when the tires of the car compress the hose. The dramatic LV waveform is the car tire running over the hose. In other words, the catheter tip has occluded the vessel and no forward coronary blood flow exists. When the ventricles squeeze during systole, the muscles compress the arteries/arterioles/capillaries. That is why we see the ventricular-type waveform, because it is reflecting the ventricle squeezing. However, as dramatic as this waveform is, THERE IS NO CORONARY FLOW! It also accounts for another reason why we usually see ventricularization during cannulation of the left main, because the left anterior descending artery (LAD) has more muscle mass surrounding it than the RCA (refer to our previous articles on diastolic filling). What is supposed to be corrected? Since we wouldn’t know at the time whether the waveform is caused by a lesion or a catheter placement against the wall, the catheter should be removed into the aortic root until the operator can analyze the situation further.1 Dr. Melvin Judkins had been quoted as saying, “No points are earned for coronary catheterization — the catheters know where to go if not thwarted by the operator.”2 If catheter misplacement caused the waveform, then gentle repositioning may help resolve it. After the catheter is re-engaged, pressure waveforms can be looked at, and a small amount of contrast injected to see what the operator is facing. You may see some operators that will continue gentle contrast injection as the catheter is being withdrawn, which may allow the lesion to show up on a few frames of the cine. There are many ways that the operator can handle an engaged catheter that results in these two waveforms. The nurse/technologist responsibility is to be able to identify these waveforms and let the physician know. The patient’s life and well-being may depend on it. Next month, we will address questions about anticoagulants in the cath lab from an application perspective.

1. Baim DS, ed. Grossman’s Cardiac Catheterization, Angiography, and Intervention. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2006. 2. Judkins MP. Selective coronary arteriography, a percutaneous transfemoral technique. Radiology 1967;89:815.