Acute Aortic Dissection is a potentially life threatening vascular emergency. We’ve previously discussed the classification of dissection and briefly looked at conservative management in the form of impulse control. The idea is to reduce blood pressure and slow the heart rate to prevent worsening of the dissection either until it can heal or until surgical correction can be performed.

But, what’s the best way to monitor blood pressure in these patients? My practice is to place a radial arterial line in any patient with an acute aortic dissection. But, is a cuff adequate? Which arm should be used? Academic Life in Emergency Medicine (ALiEM) recently featured a post looking at the evidence to possibly answer these questions.

Classically, these patients will have different blood pressures in each arm, although this is not a universal finding. This difference may be predictive of dissection, but a 2018 study found that “any recorded difference in volume/force [of the pulse] or difference in obvious signs of malperfusion” was better at diagnosing acute aortic dissection. In the case of different systolic blood pressures in each arm, the higher of the 2 should be used to guide antihypertensive therapy. So, check both arms with a cuff and place the arterial line in the side with the higher pressure. You can continue to spot check the contralateral arm with a cuff as well.

There is a way to do a CABG without going on cardiopulmonary bypass (CPB) and arresting the heart. It’s called Off-Pump Coronary Artery Bypass Grafting, or OPCABG. How do they do it? Why do they do it? Well, the why is easy. CPB has a lot of downsides to it, including risks from cannulating and risks from the CPB pump itself, and so if you can avoid it, you avoid those risks. However, not every patient is suitable for OPCABG, so the CPB isn’t going away just yet.

How do they do it? Surgeons use a special stabilizer device to hold the heart in place, allowing it to continue beating while the part where the surgeon is working is held still and stable. I assume that it is much easier to suture on something that isn’t moving! (After spending a semester in school first-assisting in cardiac surgery, I’m not sure I could suture coronary arteries on a heart that was perfectly still, much less one that was beating!)

In this great Instagram post, Dr Rishi Kumar not only explains this process in more detail, but shows you a great video of the process itself.

Although there are newer devices out there to augment cardiac function and serve as temporary ventricular assist devices, the mainstay device is still the Intra-Aortic Balloon Pump (IABP). It’s a relatively straightforward system using a balloon inflating and deflating in the aorta in time with the cardiac cycle and it offers both unloading of the LV and enhancement of coronary perfusion. Over the years, the technology of these devices has improved dramatically. When I was a CVICU nurse back in the day, we used to have to constantly adjust the timing on the pumps to maximize the effectiveness. Nowadays, the computer processing is so good, in my experience, it’s really hard to improve on the timing. But, it’s still good to know how, and how to troubleshoot the device.

This Twitter thread from Matt DiMeglio (@Matt_DiMeglio) does a great job of reviewing how the IABP works, the physiology behind Intra-Aortic Balloon Counterpulsation (why the IABP helps), what the waveforms mean, what the alarms mean, how to troubleshoot, and generally everything you need to know about IABP while on your Cardiac ICU rotation. These devices will be found in CCUs as well as CVICUs, and I’ve even used them in the NSICU! This is a great thread to read and bookmark for the next time you find yourself dealing with the balloon pump.

So, I’m on a roll with student-inspired posts. This is something we covered in class recently when talking about interpretation of 12-lead ECGs, the concept of axis deviation. An Instagram Account that I just discovered called Master Your Medics has a nice post on understanding what axis deviation is. I think this can be confusing if you’re just learning to read 12-lead ECGs. You may never have even heard the term “cardiac axis” much less “axis deviation” before. So, what is it and why does it matter?

That’s pretty basic, but that really does boil it down simply. How do you determine what your axis is on a 12-lead? That’s a little more involved, but there are some really simple techniques. I could go into a lengthy discussion here, but why reinvent the wheel? As usual, our friends over at LITFL have us covered! Mike Cadogan and Rob Buttner do a great job of explaining the cardiac axis and how to determine it for yourself (without relying on the ECG machine to tell you).

One of my pet peeves in the ICU is when we just randomly slap ECG electrodes on patients in “roughly” the right spot. The one I see done most often is the brown electrode (the precordial lead for the monitor). It’s often just slapped down wherever. In fact, I remember being taught the mnemonic devices “smoke over fire,” “snow on grass,” and “white on the right” when I was a new nurse to remember the limb leads. But the one that I was taught that is horribly incorrect is “brown is the sh*t in the middle.” Thus, it didn’t really matter where the brown electrode was placed.

But it does matter. There’s a lot of useful info that you can get if the leads are positioned correctly. And there are other ways to arrange all the leads on the monitor. Some of these will get you different information. One of these configurations is the Lewis Lead. Credited to Welsh cardiology Sir Thomas Lewis (it’s too bad I’m not Sir Bryan Boling…), this is a way of arranging the ECG electrodes to better detect atrial activity, such as amplifying the waves in atrial fibrillation.

Robert Buttner and Mike Cadogan over at Life in the Fast Lane have a great post describing the Lewis Lead, it’s history, it’s usefulness, and how to do it right. Check it out. And please, stop just putting the brown electrode wherever.

We’ve talked recently about the classification of aortic dissection based on location. But what if you want to be more specific about the location of an aortic injury? The Society of Thoracic Surgeons (STS) break the aorta down into 11 zones. Rishi Kumar explains the breakdown in this excellent diagram.

We classify aortic dissection as ascending and descending, but there are actually classification schemes with slightly more nuance. The two main classifications are Stanford and DeBakey. Stanford is broken into A (ascending) and B (descending). DeBakey into I (all the way from the ascending down the arch as well), II (ascending only), and III (descending only). Understanding these classifications makes it easier to visualize what’s going on when the CT surgeon calls to admit a patient to the ICU. Sometimes these are surgical emergencies (most commonly Stanford A or DeBakey I and II) but a lot of the time they can be managed conservatively. Conservative management is mainly with impulse control, by keeping the heart rate and blood pressure down. Blood pressure control makes intuitive sense, reduced pressure means less force on the wall of the aorta weakened by the dissection. Heart rate control is a little less obvious, but if you’ve ever seen a heart beating in an open chest, you know that with every beat, the heart twists slightly. This leads to shearing forces that can exacerbate the dissection.

Impulse control may be accomplished by an infusion of esmolol, but increasingly, drips like nicardipine are added for blood pressure control, as esmolol typically doesn’t really control profound hypertension all that well. Esmolol commonly requires a larger volume of fluid because of the dosing and way the drip is made. So, nicardipine in combination with intermittent dosing of metoprolol may be beneficial in patients who can’t tolerate the larger IV volumes.

Count Backwards from 10, has this nice graphic to sum up aortic dissection classification.