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Artificial Heart Recipient Has No Pulse
laggist writes "A heart patient in Singapore has been implanted with an artificial heart that pumps blood continuously, allowing her to live without a pulse. From the article: '... the petite Madam Salina, who suffers from end-stage heart failure, would not have been able to use the older and bulkier models because they can only be implanted in patients 1.7m or taller. The 30-year-old administrative assistant is the first recipient here to get a new artificial heart that pumps blood continuously, the reason why there are no beats on her wrist.'"
The story is light on details, but an article from last year in MIT's Technology Review explains a bit more about how a pulse-less artificial heart works.
The easiest way of moving a fluid is with a fan. It's trivial to make an artificial heart that works like that, but it has a disadvantage; the fan blades damage the blood cells. A few devices that work like this have been around for a while for emergency use (e.g. if the heart stops in the middle of an operation), but they can't be used for more than a couple of days without killing the patient (having a few blood cells killed is generally better than having no blood flowing, so they're fine for short-term use). I don't know how they solved that problem for this machine.
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Most of these artificial heart patients end up dying of strokes, caused of course by blood clots. It's theorized that such clots are easier to form in a pulse-less environment of steady-flow than in an environment where the blood is being "shaken" a bit, ie the pulse with each heartbeat.
occultae nullus est respectus musicae - originally a Greek proverb
Speaking as a biomedical engineer, there are no significant systems that we know of that require a varying pressure of blood to function correctly. The pulse as the blood gets pumped stretches the arterial and capillary walls slightly, but that's about it. Very few cells in the body experience the effects of the pulsing pressure to begin with, and those tend to be ones that can function despite the pulse rather than because of it.
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Automated external defibrillators, such as the Physio-Control LifePak 500, will only administer a shock if they detect a valid shockable rhythm, i.e. ventricular fibrillation. This AED will not shock anyone or anything that does not have that rhythm present.
Manual external defibrillators, such as the Physio-Control LifePak 12, which may only be used by EMT-I or EMT-P (Paramedics) in my home state, can be used to administer a shock regardless of the presence or absence of any cardiac rhythm. This requires a manual override, and from what I have seen, is used even less often than the precordial thump.
Cardiac compression is the thin end of the wedge; Defibrillation would be real bad news.
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some blood machines use a system where the tube holding the blood is squeezed repeatedly by a rotating disk (there are like pegs on the disk and as they pass over the tubing the squeeze it like you do with toothpaste.) Advantage I understand it is its sterile since no part of the motor or other components actually contact the blood. Not sure if its a similar system or not.
I would bet that an EMT, nurse, or doctor would realize something's going on in the chest upon auscultation of the apices, and in a triage situation you don't bother with the non-breathers until the bleeders are taken care of.
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This device is bladeless. In fact, one of the major advantages of this artificial heart compared to the traditional ones, is that this damages less blood cells than all other artificial "pulsed" devices. It has other benefits, like smaller size and less energy consumption. Overall, it's a greatly improved system.
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The first in Singapore. The technology has been around and in use elsewhere for years, as evidenced by older articles explaining it (and I remember reading about this a while back).
***Well, for one, how do these people get their blood pressure measured?*** Good question. It would appear they don't -- at least not with a sphygmomanometer that depends on the Korotkoff sounds generated by cutting off pulsating blood flow. And they won't have a pulse either. Those characteristics would normally be symptomatic of being dead. Or maybe one can pump up the blood pressure cuff and listen for a single -- hopefully loud and distinct -- thunk when blood starts flowing. OTOH, not having a pulse or measurable blood pressure beats all hell out of having a pulse and not being functional. I can't imagine what they are going to put on her MedicAlert bracelet.
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A pair of Peristaltic pumps will create a continuous flow and function significantly similarly to an actual heart. Many heart-bypass machines are designed like this.
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She is holding a Heart Mate II pump...most of our patients get this model...and NONE have a regular pulse. Funny since this is just breaking news and St Lukes Heart Transplant do it day in and day out, for a loooong time.
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the technical term for those wondering (this is/. afterall) is paristaltic pump
The problem with stiff arteries is that they conduct the pulse wave a lot faster. As it is reflected at junctions and narrow passages in the arteries, it can then get back to the heart while the aortic valve is still open. The heart then has to work against the higher pressure, which increases the workload and eventually leads to heart diseases.
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Breathing. One of the checks is not just a pulse, but breathing as well.
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According to the MIT write-up, you still have blood pressure. The device would pump more or less blood based on your body's need at the time. What you would NOT have is a systolic/diastolic reading. You'd have one pressure reading. No more 110/70 reading, perhaps a 85mmHg in its place.
This was covered in the article, the pump works on a feedback mechanism to define how fast to pump, but the description didn't make much sense to me as IANAHS.
APK likes to ask for responses to the same things over and over. Maybe he just likes the responses?
The article (the second link) specifically mentions that the flow rate increases when the return rate increases meaning that yes, it can keep up, and may even out-perform her old heart in terms of flow.
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BP is measured with by ultrasound - the BP cuff is inflated to 80% of its maximal capacity and slowly pressure is released until the first sound, a soft sound not unlike the whirling hum of a hairdryer, is auscultated. Normal BP for adults is 105-110/70-75; LVAD patients generally have a blood pressure of 80 - there is no "top" or "bottom" number, but it would be most akin to the diastolic.
My partner was an ICU nurse and used continuous flow VADs (Ventricular Assist Device) for years.
Here's an article from 2000: http://circ.ahajournals.org/cgi/content/abstract/circulationaha;101/4/356
There is some controversy about continuous flow, but the notion is that most of the body experiences nearly continuous flow, anyway.
Implanted continuous flow notes from April: http://www.ncbi.nlm.nih.gov/pubmed/19324130
And another from 2008 implying that pulseless does not matter:
http://www.ncbi.nlm.nih.gov/pubmed/18442710?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.Pubmed_Discovery_RA&linkpos=1&log$=relatedarticles&logdbfrom=pubmed
Open one of your eyes and shine a light in it. If the pupil constricts, you're alive. Of course, if you have a condition that makes your pupils NOT constrict, you're in some deep trouble!
But these artificial hearts are NOT for permanent implantation, they're to keep you alive until a donor heart can be found. If you have an artificial heart you should NOT be drinking; you're WAY too ill.
My cousin contracted a virus of some sort in her heart, and had an artificial heart implanted for several months. She has a live, donated heart now.
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It works like your esophagus does when swallowing.
Read "Superluminal", by Vonda McIntyre. It's a sci-fi story about a woman who gets a turbopump heart that doesn't beat -- not because she's sick, but because it's a necessary part of becoming a starship pilot. Romance and heartbreak ensue.