Mr. Cheney’s Heart
This last week the newspapers reported on yet another chapter in the story of Dick Cheney’s ongoing struggle with heart disease. The former vice president was admitted to George Washington Hospital in June for “chest pain” and has now announced that he underwent surgical placement of a heart pump.
Mr. Cheney’s long-running saga of cardiac issues reads more like an exhaustive treatise on cardiovascular disease than a personal biography. He suffered his first heart attack in 1978 at the tender age of 37 and with that gave up his longstanding smoking habit. Just ten years (and two heart attacks) later he underwent coronary artery bypass surgery. Since that time he’s had at least one more heart attack, episodes of unstable angina, two percutaneous interventions (angioplasty and stents), congestive heart failure (CHF), peripheral arterial aneurysm repair, atrial fibrillation, and the placement of a defibrillator. I now almost need to consult my cardiology textbooks to conjure up any heart ailments he hasn’t had. Let’s see . . . as far as I can tell he’s yet to develop Chaga’s disease or peripartum cardiomyopathy.
The former veep is now the proud owner of a HeartMate II ventricular assist device (VAD), a small machine that serves as an accessory pump in the chest to relieve pressure on his ailing heart. Requiring an open thoracotomy (“cracking the chest”), the $100,000 VAD has proven quite effective at dramatically improving patients’ symptoms and extending their lives to the point where they can undergo cardiac transplantation. Recent published studies also suggest that the device can serve as a stand-alone therapy (referred to as “destination therapy”) for CHF rather than just a bridge to transplant, and there are many reports of patients doing so well with the VAD that their own heart has the ability to heal to the point that the device can be removed.
The pump itself is a fascinating marvel of engineering. The VAD sits inside the chest and draws blood from the left ventricle of the heart through a large diameter tube. A magnetically driven corkscrew mechanism serves as the pump and allows the device to function with only one moving part, decreasing the likelihood of malfunction over time. The blood is then propelled into the base of the ascending aorta and continues on to the rest of the body.
Now here’s the fascinating part. The VAD cycles blood to the aorta in a continuous fashion. As you may have already surmised from inspection of your own body, the pump most of us were born with propels the blood in a pulsatile manner, resulting in the familiar pulse found in the wrist, neck and elsewhere. Here’s what Wikipedia has to say about this design:
“A side effect is that the user will not have a pulse, or that the pulse intensity will be seriously reduced, and will need to carry documentation saying that the lack of a pulse does not mean that they are dead.”
While I’m normally quite fond of the reliability of Wikipedia in the realm of medicine, I was a little skeptical about the whole issue of documentation. I would have thought that the owner of this type of device could be taken at their word that they are still alive and would not need to produce some type of written verification. I can imagine that late night comedians could have a field day with this tantalizing bit of information about Mr. Cheney, a man many left-leaning pundits already accuse of being among the undead.
In order to clarify the purported need for proof-of-life I reached out to an expert on the matter. Dr. Mohammed Quader is a cardiothoracic surgeon who has long been a member of the heart transplant team at the Nebraska Medical Center and is someone who has implanted a number of these fascinating pumps. He told me that these patients are indeed lacking in the usual arterial pulse but appear to function remarkably well despite the aberrancy. It turns out that the presence of pulsation is not necessary to normal physiological function and that blood flow at the level of muscles and organs is non-pulsatile anyway (the oscillations of systolic and diastolic pressure become dampened as blood progresses from large elastic vessels like the aorta and brachial artery to the small arterioles and capillaries).
Since the presence of a pulse is requisite for the use of a sphygmomanometer (blood pressure cuff) a nurse or medical technician would have to use a Doppler probe in order to determine the patient’s mean arterial pressure. Dr. Quader states that patients are not actually required to carry around the documentation cited by Wikipedia, but that the patient and their family members are educated about the lack of pulse and can pass this information along to emergency medical providers.
One of the current limitations to the existing devices relates to their supply of electricity during normal function. While the device Mr. Cheney owns will be encased in his rib cage he will still have a power cord connecting the VAD to an external battery source. Patients need to carry with them the battery needed to power the device as well as a back-up battery to employ the moment its needed—losing power to a VAD is a slightly more serious problem than having a cell phone battery go dead.
The power cord itself is a source of some of the difficulty with the VAD as it serves as a conduit for bacteria to potentially enter and infect the space occupied by the device. This problem will likely be remedied in the not-to-distant future by technology that enables wireless transmission of electrical energy from a battery pack outside the skin to the implanted VAD without the need for a cord.
My personal experience with the device is limited to a solitary patient of mine who recently received a HeartMate II and whom I saw in my clinic a couple of weeks ago. She suffers from dilated cardiomyopathy and has had declining health over the course of the last few months despite my best efforts. I sent her to the Nebraska Medical Center to be listed for heart transplantation and as her condition worsened the transplant doctors decided to offer her the VAD. Her quality of life improved dramatically after she received the device and she is now back to a fairly healthy level of daily activity. I admit it was a little spooky listening to her chest and not hearing the familiar lub-dub that accompanies most of my living patients. She remains on the cardiac transplant list but should do quite well for the foreseeable future.
Others have done well with such devices for several years. The longest surviving owner of a VAD was one Peter Houghton, a psychotherapist and author who received an early-generation device in 2000 and went on to live 7 more years with the same device during which time he completed a 91 mile charity walk, published two books, lectured widely, hiked in the Swiss Alps and the American West, flew in an ultra-light aircraft, and traveled extensively around the world.
While I don’t foresee Mr. Cheney spending too much time in the Alps he’ll probably recover from this episode as quickly and gracefully as he has from nearly everything else. And, despite his lack of heartbeat, I don’t imagine he’ll miss a beat as he resumes his usual cantankerous vexing of the current presidential administration and liberal pundits.
Joseph, You make good points about future technology and you are right on track. How about this for a futuristic device? A VAD that not only provides real-time pressure measurement but also transmits to an out-of-body monitor (perhaps something as simple as a smart-phone) so that the patient can access their own BP at any time. Take it a couple steps further. Not only could the VAD measure mean arterial pressure but also sense LV filling pressure (something akin to PCWP or LVEDP, although those terms don't actually apply to a ventricle with no real diastole) and transmit that info. Furthermore, such a device could be wirelessly (Bluetooth) slaved into a subcutaneous pump (similar to insulin pumps) that could trigger small releases of diuretic or inotropic medication as needed to maintain the optimum filling pressure. The system would provide instantaneous alerts to the medical team if parameters become sufficiently abnormal that the patient should be brought into the hospital before full-blown congestion occurs. All this technology already exists or is in development in one form or another. The companies that produce rhythm devices (pacers, ICDs) have already incorporated much of this technology into their products. It shouldn't be too much longer that such devices are made available. Good ideas. Thanks. Dr. VDG
Molly, Good question. You would think that the ventricular contraction is no longer needed if the LVAD is sucking the blood out of the left ventricle (LV) and pouring it into the aorta. In order to get you the authoritative response I consulted a friend of mine at NMC. Dr. Dumitru is a cardiologist who heads the transplant team for the state of Nebraska and has had considerable experience with both cardiac resynchronization therapy (CRT, aka Bi-V ICDs and pacers) and LVADs. The policy of her team is to make no programming changes to the pacing and shock functions of the ICD. Her reasoning stems from the fact that the CRT is still beneficial to the function of the right ventricle (RV), which as you know provides the filling pressure to the LV. Without adequate RV function there would be inadequate blood in the LV for the LVAD to pump. For these patients the most efficient scenario is a healthy RV (thanks to pacing) and an LVAD to assist the LV. Thanks for the question. Dr. VDG
Patients who have a ventricular assist device generally still have ICD's. LVADs provide support for only the left side of the heart, the right side still functions without assistance and it is important to maintain a normal (as much as possible) electrical conduction system (which is what the ICD/PM does).
Thank you for the great article. You may consider correcting the Wikipedia article with all of your spare time! I am fascinated by this kind of biotech and what the next stage may be. You mention the idea of wireless transmission to the unit as a great power/infection solution, but I wondered about the whole blood pressure issue. Does it cost a lot to use Doppler to take a reading? It sounds expensive, but maybe those weather stations just act like it is. I guess my big question revolves around maintenance costs once the device is installed. I wonder if at some point they could get the VAD itself to provide the blood pressure information, provided two things are true. 1) Patients carrying these things around in their chests need very regular BP checks, and 2) The Doppler checks are expensive. I am not an engineer, but it seems like if the device is moving the blood around, there might be a way for someone really smart to get it to tell us more specifically what it is doing. Again, if the Doppler is no more expensive than the cuff, it is a non-issue, but with medical costs where they are, an already expensive solution could be served by finding creative ways to engineer away from additional costs.
I suspect the cause of Cheney's cardiovascular problems is, in actuality, a vast right-wing conspiracy to convince the world that said Mr. Cheney does, in fact, have a heart. Thank you. I'll be here all week long. Please tip your waiter on your way out.
Very interesting blog... I have a few questions for you.... If these patients have had a Bi-V ICD placed,is that device removed prior to placement of the LVAD? Will the left ventricle still continue to try to contract once LVAD is functioning?