The Heart: An Incredible Electric Machine

A quick primer on the electrical system of the heart followed by two major breakthroughs in pacemaker technology this year.

What makes the heart beat? Learn about the conduction system, an incredible machine.

A leadless, subcutaneous defibrillator makes the list of 5 biggest medical breakthroughs of the year.

Boston Scientific has begun marketing a FIRST-OF-ITS-KIND DEFIBRILLATOR after receiving FDA approval in September. The implantable device, which protects against sudden cardiac arrest, was developed by a California firm purchased by Boston Scientific and is expected to be a financial win for the Natick-based company. Unlike others on the market, the S-ICD does not touch the heart, instead sending electrical pulses to correct abnormal rhythms through wires implanted just beneath the skin.

http://bostonglobe.com/magazine/2012/10/27/biggest-medical-breakthroughs-year/pLJDenlFAN3XFwwsxfU7CI/story.html

No More Batteries: Piezoelectric Pacemaker Powered By The Heart

An experimental device converts kinetic energy from beating hearts into electricitythan can power a pacemaker, meaning the chance for no more batteries in the future, according to a talk at the American Heart Association’s Scientific Sessions 2012.

The study is preliminary but a piezoelectric approach is promising for pacemakers because they require only small amounts of power to operate. Batteries must be replaced every five to seven years, which is costly and inconvenient.  Piezoelectricity might also power other implantable cardiac devices like defibrillators, which also have minimal energy needs.

“Many of the patients are children who live with pacemakers for many years,” said M. Amin Karami, Ph.D., lead author of the study and research fellow in the Department of Aerospace Engineering at the University of Michigan in Ann Arbor. “You can imagine how many operations they are spared if this new technology is implemented.”

Researchers measured heartbeat-induced vibrations in the chest. Then, they used a “shaker” to reproduce the vibrations in the laboratory and connected it to a prototype cardiac energy harvester they developed. Measurements of the prototype’s performance, based on sets of 100 simulated heartbeats at various heart rates, showed the energy harvester performed as the scientists had predicted — generating more than 10 times the power than modern pacemakers require. The next step will be implanting the energy harvester, which is about half the size of batteries now used in pacemakers, Karami said. Researchers hope to integrate their technology into commercial pacemakers.

Two types of energy harvesters can power a typical pacemaker: linear and nonlinear. Linear harvesters work well only at a specific heart rate, so heart rate changes prevent them from harvesting enough power.

In contrast, a nonlinear harvester, the type used in the study, uses magnets to enhance power production and make the harvester less sensitive to heart rate changes. The nonlinear harvester generated enough power from heartbeats ranging from 20 to 600 beats per minute to continuously power a pacemaker. Devices such as cell phones or microwave ovens would not affect the nonlinear device, Karami said.

http://www.science20.com/news_articles/no_more_batteries_piezoelectric_pacemaker_powered_heart-96003

 

What is a Heart Attack?

Figure A shows a heart with dead heart muscle caused by a heart attack. Figure B is a cross-section of a coronary artery with plaque buildup and a blood clot.  

A nice image from the National Heart Lung and Blood Institute of what a heart attack  is.  This represents a rather large heart  attack because of insufficient blood from the LAD or the widow maker. This type of a heart attack would  typically cause changes in the EKG. This would create a STEMI or ST segment Elevated Myocardial Infarction. This means likelyhood is a heart attack involving the full thickness of the heart wall. When this occurs we usually note changes in the EKG.

See   Medical terms you should know for a description of the EKG changes that occur with this type of a heart attack.  

 

Know your Nitro and Save your life

Nitroglycerine  Facts

One thing that always surprised me in cardiac rehabilitation was the understanding of using Nitroglycerin (nitro). I think over the years I saw and heard every way imaginable to ensure nitro tablet wouldn’t work if needed. Or the other one is when patients would carry it for years and then not use it when it is most appropriate to use. The take home message is if you are having discomfort that you suspect is heart related use a nitro ASAP.

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How Nitro works:

Nitroglycerin  dilates blood vessels that supply the areas of the heart where there is not enough oxygen thereby delivering oxygen to the heart tissue that needs it most.  The dilation of  veins and arteries  reduces the amount of blood returning to the heart so that the heart does less work and requires less blood and oxygen. Dilation of the arteries  lowers the pressure in the arteries against which the heart must pump. As a consequence, the heart works less and requires less blood and oxygen.

How to store Nitro:

Here is the thing Nitro is a very volatile compound. It breaks down rapidly with light, heat, oxygen, time and exposure to plastic. It is packed in a glass vial because plastic will leach the active ingredient out of it and all you have left is the inert ingredients that hold the tablet together. Therefore don’t transfer it to a container that is plastic, don’t put a couple in a baggy and put them in your wallet. Yes it is a pain in the butt to carry the bottle everyday, but find a way, or use a metal nitro vial which you can wear around your neck.

Heat will break down the nitro tablets. If you carry your Nitro in your pants pocket every day the heat from your body will gradually make the nitro less potent.  What I teach patients is to take a good marker and write on the bottle the date three months from when they started to carry the bottle. That is when it should be considered to replace. Sometimes it can go six months, but if you look at the bottle…hold it up to the light, don’t open it…and the tablets are looking powdery or crumbled….then replace the bottle. If you leave them in your pocket and they go through the dryer…time to replace. If you leave them in your car and your car is 100* or more…replace the bottle. That was a common one…”I leave them in the glove box in my car.”  NO NO NO!

If you have opened the bottle you have exposed the tablets to oxygen. Oxygen breaks down the nitro. Once the bottle has been opened, label the bottle for six months from the time  you opened it. Replace the bottle at six months. A story I would frequently hear that would make me cringe would be when a patients loved one or child would say ” I poured a couple in a paper cup and have them in my cupboard in case they need one while at my house”…UHG!!!! Won’t work sorry!

The bottle is brown to prevent sunlight from destroying the tablets as well. Don’t transfer them to any other bottle, there is a reason they come this way.

When to use Nitro:

The most common mistake in using nitro is when patients would tell me the pain wasn’t bad enough to use it.  The instructions for nitro don’t say wait until the discomfort is 9 out of 10, the instructions are to use the nitro if you have heart symptoms that do not go away with rest.  This means any heart discomfort, no matter how minor if is present for 5 minutes, would indicate using the nitro.  If you wait until you are really in pain, you probably will have damage done to the heart. The point of this drug is to prevent the damage to the heart by improving the blood flow preventing damage from occurring.

  • Sit down
  • Place one tablet under the tongue – most people experience a burning or tingling feeling under the tongue, a headache, a flushed feeling….If you experience this you should always experience this, as this indicates your nitro is fresh.
  • Wait 5 minutes – if the symptoms resolved rest a bit then gradually become active again
  • If the symptoms persist use a second nitro table, again wait 5 minutes, if needed take a third 5 minutes later
  • If you took a third nitro and still have symptoms call 9-1-1.Try to do some deep relaxing breathing, and thinking try not to panic. It’s a good time to use those relaxations skills.
  • Chew an adult strength aspirin while you wait for paramedics

One discussion I frequently have with patients goes as follows: You may carry your nitro faithfully for years and never need it, but if and when you do need it, you want it to be fresh so it can work. On the other hand some will need to use occasional nitro. This isn’t a bad thing. Your physician prescribed it for a reason. Use it!!!! There are common times when people need one…Exposure to cold air, Exertion that is strenuous, Emotional Stress, and after Eating a large heavy meal. Where the medical community get concerned is if you are requiring 2-3 nitro to clear your symptoms, if you are having more frequent symptoms, or if your symptoms are coming on at rest or waking your from your sleep. The escalation in symptoms should be reported to your physician ASAP.

Keep a log of your nitro  use.  Put on your log, the date, what you were doing when the symptoms occurred, and how many nitro it took to clear the symptoms. When you have a followup appointment with either your cardiologist or your primary care physician present them with the log. Sometimes we are able to find a pattern, do your symptoms come on at a certain time of day? Thus we can probably adjust medication timing to prevent this. Do they come on with a certain level of exertion? We call this your angina threshold and we watch to see is the threshold improving or worsening. Often through exercise we can improve the angina threshold.

What about long acting nitro?

There are long acting nitroglycerin medications that slowly release nitro into your system throughout the day. These are usually taken during the hours you are up and active. Rarely are they used twice a day, as your body needs a period of time in which it is free of nitro, or else it gets to where the nitro doesn’t work as effectively. It is still ok to use the fast acting nitro if you are on this medication.

What about the headache from taking Nitro? 

Take a Tylenol.  The headache won’t kill you but the heart attack might.

ICD’s: Resources, Decision Making, and What to Know

An ICD is an implantable cardiac defibrillator. They are used for people who are high risk sudden cardiac death due to heart arrhythmias  of  ventricular tachycardia or ventricular fibrillation. They are often implanted as a preventative measure when the heart has a poor pumping ability as this makes one prone to arrhythmias. If the ejection fraction (pumping ability) is 30% or less and doesn’t show signs of improving your healthcare provider may consider implanting one.

Special care should be placed not to put excessive strain on the shoulder, arm and torso area where the ICD is implanted. Doing so may damage the ICD or the leads going from the unit to the patient’s heart. For this reason strength training with heavy repetitive weights is often discouraged. The exercises which would potentially damage the leads involves exercises with the arms overhead, such as a Military or shoulder press, seated fly’s,overhead triceps press. By heavy weights we are talking about weights upwards of 100 lbs or more with repeated repetitions and multiple sets. The wiring goes under the first rib, repeated bending and stress to the wires in this area can damage the leads. If your work involves this type of activity be sure to discuss this first with your cardiologist.

Exercise Advice:

  • Exercise with a friend or family member who is familiar with your condition and knows what to do in the event of an emergency.
  • If you exercise at high intensities, you should make sure you have a specific guideline from your cardiologist about your heart rate range. If the heart rate is too high the ICD may sense it as Ventricular Tachycardia. Wearing a heart rate monitor can help you to watch your heart rate range and avoid exercises that spike the heart rate up into the threshold in which the defibrillator is programmed to respond. Your Cardiologist can adjust your ICD settings to recognize the difference between a normal increase in heart rate from exercise and that associated with an abnormal heart rate or rhythm. You should include a low-level 5 to 10 minute warm-up and cool-down phase for aerobic exercise (i.e., walking, cycling) to allow for a slow and steady increase in heart rate.
  • The ICD can be affected by magnetic or electrical fields. You should avoid this and opt for something simpler such as the sum of skinfolds. Heart rate monitors are unlikely to cause any problems in the gym setting. Avoid Bio electric Impedance devices which are used to measure body fat.
Decision Making:
I came across a New York Times article “A Heart Quandry”  recently with the following information. It is something to consider for anyone with an ICD.         http://newoldage.blogs.nytimes.com/2012/06/07/a-heart-quandary/

Going against strong headwinds in his own community of heart specialists, Dr. Kramer emphasizes three important issues that come about when older patients with ICDs face battery depletion.

First, he asks heart doctors to re-evaluate whether the patient still benefits from the ICD. Perhaps, the original heart problem has improved?

Second, he points out that a patient’s experience living with the device may have changed their mind about keeping it active. Perhaps, a patient with inappropriate shocks no longer wants the device?

Third, since the original implant, a patient may have changed their goals of care. Many patients no longer desire life-sustaining shocks—for whatever reason. It’s their choice; but they aren’t often asked.

You may wonder why such obviousness isn’t the norm?

It’s because our healthcare system imparts significant barriers. Dr. Kramer nicely explains two important hurdles. One is that healthcare in the US is fragmented, especially for the infirmed and elderly. Patients may have many doctors, and care is often not well-coordinated. This means, an installer, a proceduralist like me, is left discussing end-of-life care with patients immediately before ICD surgery. That’s not good. I am married to a hospice doctor, so I sort of know how to manage these conversations. This is not the norm for procedure-oriented heart doctors. The other barrier to getting the elderly the best care is our system’s misguided incentives. In our current fee-for-service system, I am rewarded for doing, not discussing not doing. In fact, not doing stuff is very risky—both legally and professionally (ie. loss of referrals.)

Finally, Dr. Kramer and his colleagues call for heart doctors to take the lead in starting “the conversation” with ICD patients. He wants us to share the decision of using invasive, potentially dangerous or ineffective care with the patient. He also asks the scientific community to study the outcomes of patients who undergo elective ICD generator changes. These should not be controversial recommendations.

It’s a huge mistake to equate this kind of smart thinking to rationing. Aligning evidence-based care, especially potentially burdensome surgery in elderly patients, with the goals of the patient is not rationing.  It’s moral, ethical and obvious.

Resources:

There are issues with ICD that patients struggle with. These include the comfort of the ICD, the cosmetic appearance,the stress of having it fire, frequency of battery replacement, leads wearing out, and it working appropriately. I have included a few great resources to help you in living with an ICD.

Sudden Cardiac Arrest Association                     http://www.suddencardiacarrest.org/aws/SCAA/pt/sp/home_page

Powered by Inspire      https://www.inspire.com/groups/sudden-cardiac-arrest-association/topics/living-with-an-icd/

Boston Scientific       http://www.bostonscientific.com/lifebeat-online/live/icd-patients.html

Beta Blockers

I bet you were discharged out of the hospital on several new medications. I am not a pharmacist but can certainly talk about the common medications for heart disease and their side effects. It is important to understand what medications you take and what they are supposed to do, as well as what potential problematic side effects to be watchful for.

Beta Blockers - Beta blockers work by reducing the heart rate and causing the heart to beat less forcefully. They also relax blood vessels, which lowers blood pressure and allows blood to travel more easily to all areas of the body.

Common Beta Blockers: Atenolol, Proprandalol, Metoprolol, Bisoprolol, Carvedilol

Side effects:

  • A slow heart rate  - this is what they are supposed to do slow the heart rate but sometimes it slows too much. Heart rates in the low 40′s or less should be reported to you physician.  When sleeping usually your heart usually beats even slower so rates in the 20-30′s are a problem
  • Low blood pressure- again this is what beta blockers are supposed to do, but if your blood pressure is less than 80/40 or you don’t feel well at the level you are at report to your doctor as soon as possible.
  • Fatigue – It takes about 30 days for your body to get used to this medication. If you are so fatigued that you cannot perform your daily functions contact your doctor.
  • Cold hands and feet
  • Dizziness – Get up from seated positions slowly, wiggle your legs before standing if you have been seated for a long length of time
  • Lightheadedness or fainting, which can be a sign of dangerously low blood pressure. Again get up slow from bending over, seated positions and do a good cooldown with exercise to prevent this side effect.
  • Worsening of asthma – if you have asthma make sure your doctor aware as this medication can make it worse.
  • Depression
  • Signs of heart failure, such as rapid weight gain, swelling of the hands and feet, and shortness of breath
  • Sexual problems erectile dysfunction is very common and low sex drive. Don’t be afraid to mention this to your physician.
  • Masking of the signs and symptoms of low blood sugar. If you have diabetes measure blood sugar frequently before and after exercise.
  • Exercise intolerance sometime the heart rate is so blunted from this medication that it cannot rise enough to pump blood to the exercising muscles we call this chronotropic incompetence. You should see your heart rates rise 10-20 points while exercising or more. If you feel like you can’t progress your exercise intensity without feeling fatigue, weak or short of breath this may be the cause.

Palpitations May Signal Future Heart Rhythm Problem

Palpitations are common following a heart event, they can be dangerous if they are due to atrial fibrillation.

Here are  AFib symptoms:

A fluttering feeling in the chest
Chest pain or pressure
Feeling out of breath
Feeling weak or tired
Dizziness and sweating
Feeling faint or lightheaded

How Can Atrial Fibrillation Be Prevented?

Following a healthy lifestyle and taking steps to lower your risk for heart disease may help you prevent atrial fibrillation (AF). These steps include:

  • Following a heart healthy diet that’s low in saturated fat, trans fat, and cholesterol. A healthy diet includes a variety of whole grains, fruits, and vegetables daily.
  • Not smoking.
  • Being physically active.
  • Maintaining a healthy weight.

If you already have heart disease or other AF risk factors, work with your doctor to manage your condition. In addition to adopting the healthy habits above, which can help control heart disease, your doctor may advise you to:

  • Follow the Dash diet to help lower your blood pressure.
  • Keep your choleesterol and triglycerides at healthy levels with dietary changes and medicines (if prescribed).
  • Limit or avoid alcohol.
  • Control your blood sugar level if you have diabetes.
  • Get ongoing medical care and take your medicines as prescribed.

Many things can trigger palpitations, including:

  • Strong emotions
  • Vigorous physical activity
  • Medicines such as diet pills and decongestants
  • Caffeine, alcohol, nicotine, and illegal drugs
  • Certain medical conditions, such as thyroid disease or anemia

Palpitations May Signal Future Heart Rhythm Problem.