the HAE series: the Cardiovascular system part II
Now that we’ve gotten through the basics (and if you missed it, you can read about it here), it’s time to look at what can go wrong within the cardiovascular system. First, there’s the changes we all experience due to normal aging. Decreased blood flow to the heart cells, fewer pacemaker cells and decreased cardiac elasticity will lead to decreased excitability (how easily the myocardium depolarizes to trigger a contraction), decreased maximum cardiac output and stroke volume (how much blood can be pumped out), less venous return (how much blood gets sent back), decreased maximum heart rate and increased resting blood pressure. Basically, the heart gets a little weaker, a little slower and a little less powerful over time.
There are also problems that can occur due to pathology. I like to look at these in three ways; problems with the Pump, problems with the Pulse and problems with the Periphery.
First, let’s talk about the Pump. As we reviewed in the Basics, the heart is responsible for pumping oxygenated blood from the left side of the heart to the body, and then returning deoxygenated blood into the right side of the heart to get sent back to the lungs. The heart relies on it’s myocardium - it’s thick muscular wall - to create this force, and when disease affects its strength or flexibility, the pump becomes less efficient. The most common disorders of cardiac efficiency include Coronary Artery Disease and Angina, Myocardial Infarction, Cardiomyopathy and Congestive Heart Failure. Lastly, there can also be issues in valve function, causing Valve Disorders.
Coronary Artery Disease (CAD)
40% of adults ages 65-74 experience Cardiac Artery Disease; 50% will develop it by age 75. Due to atherosclerosis, the coronary arteries can become narrow and, at times, blocked, causing impaired blood flow to the heart. What was once thought of as simple fat deposit problem, atherosclerosis is now understood to be an interaction between systemic inflammation and low-density-lipoprotein (LDL) cholesterol plaque that can build up in the intimal wall lining of cardiac blood vessels. This can cause periods of intense pain, called angina. While men typically describe angina as crushing chest pain, or pain down the left arm, women experience it more atypically. Some will have symptoms of gastrointestinal distress, others report dizziness, anxiety or jaw pain. Those experiencing anginal pain will consistently report, however, that it increases with exertion, emotions, extreme temperatures or after eating, and that it resolves with rest or after taking prescribed nitroglycerin. Nitroglycerin acts as a vasodilator; it makes the arteries transiently wider to allow more blood to flow to the heart. Should anginal pain not resolve after three doses of nitroglycerin, or the equivalent of fifteen minutes, it is time to call 911, as this may result in areas of myocardial cell death or myocardial infarction (heart attack!).
When conservative treatments become ineffective, or when atherosclerotic lesions cause more than 50% blockage (identified by cardiac catheterization), surgical management is often then considered. Catheter-based techniques to reduce plaque and restore blood flow are the least invasive option and typically include Percutaneous Transluminal Coronary Angioplasty (PTCA) or Percutaneous Coronary Intervention (PCI). Coronary Artery Bypass Grafting is an open-heart surgery during which the rib cage is open and a section of healthy vein (typically from the saphenous vein in the upper leg) is used to bypass the area of blockage within the coronary artery to restore blood flow to the heart. This procedure is typically more difficult to recover from and patients can expect to take up to twelve weeks to fully heal.
Myocardial Infarction (MI)
When blood flow is blocked long enough to an area of the heart, causing unmitigated ischemia, a myocardial infarction, or the infamous ‘Heart Attack,’ can develop. Typically, MIs will occur when a blood clot formed within the coronary arteries travels towards the heart and becomes lodged, blocking flow and cutting off blood to the the area of the heart it is supposed to perfuse. An MI can be small or catastrophic, and even ‘silent’ depending on the degree and location of the damage. These so-called ‘silent’ MIs make about a quarter of all cases, occur without any precipitating symptoms. If you have diabetes, you are at higher risk for these types of infarctions. Another quarter of cases will be catastrophic and the individual will die before reaching the hospital. Though there are risks of other complications from MI including later heart failure, blood clots or stroke, those who remain free of other problems within a few hours after the MI occurs have a good chance of full recovery.
The most effective way to reduce your risk of CAD and related sequelae (or mange your condition if you have already been diagnosed) is to reduce the demand on your heart. Managing your blood pressure, whether through medications or diet and exercise is the most important aspect of CAD care. Participating in regular aerobic exercise and conditioning decreases the strain on your heart not only through weight management, but by decreasing how much oxygen your body requires to function, making your musculoskeletal system more efficient. Addressing any other medical conditions, like hyperthyroidism, anemia or chronic hypoxia are also critical to address as these diagnoses in particular also cause strain on the heart. Certain lifestyle factors like smoking, stress and depression can also increase risk of CAD and should be addressed as part of your plan as well.
Cardiomyopathy/Congestive Heart Failure (CHF)
Uncontrolled CAD can eventually lead to Cardiomyopathy and Congestive Heart Failure. When the cardiac muscle becomes weaker and less efficient, blood pools within the cardiac chambers and stretches out the atria and ventricles. With this onset of cardiomyopathy, an over-stretched heart can begin to “fail” - or pump less effectively. Congestive Heart Failure is the most common reason for hospital admission in individuals over 65 years of age and can affect the left, the right or as it progresses, both sides of the heart, and can lead to problems with the filling (diastolic) or pumping (systolic) aspects of the cardiac cycle.
Left heart failure decreases the amount of blood send to the extremities, brain and visceral organs, and leads to impairments associated with decreased tissue perfusion - weakness, fatigue and decreased activity tolerance. If the blood backs up from the ventricle into the atria, it can wind up back into the lungs and can cause pulmonary edema. People experiencing pulmonary congestion typically complain of difficulty lying flat, waking up out of breath and frequent cough with frothy sputum. When the right side fails, blood flow backs up instead into the periphery. In this case, with the right heart pumping inefficiently, the right heart remains too full, and fluid backs up into the venous system, causing systemic edema - often in both legs, ankles and feet and occasionally into the abdomen. People may also experience gastrointestinal distress and weight loss.
Heart failure can be further classified as either systolic or diastolic. Systolic heart failure is more common than diastolic. In systolic heart failure, the heart isn’t able to contract as well due to the overstretched, thinning chambers, resulting in less blood pumped out with each heart beat. People in systolic heart failure will have a reduced ‘ejection fraction,’ a ratio that compares the amount of blood in the heart to the amount of blood pumped out. This value helps give a measure to how well the heart is pumping blood out. When a person experiences diastolic heart failure, the heart struggles to relax, due to thickened, stiffer cardiac chambers, preventing the heart from filling adequately during between beats. In these cases, the ejection fraction is preserved, as the heart isn’t filling well enough to change the ratio significantly. In healthy individuals, a normal ejection fraction is between 50-70%; in cases of borderline CHF, this ratio is reduced to 41-49% and symptoms may become noticeable with activity and in more advanced cases, the ejection fraction drops under 40% and symptoms may be now be noticeable at rest.
The goal of CHF management is to keep the system ‘compensated.’ By reducing salt intake, under 2000 mg/day, and taking medications like beta blockers, diuretics and other anti-hypertensive drugs, the workload on the heart can be reduced to slow progression of the disease. Daily monitoring of signs and symptoms can allow people with CHF to quickly identify signs of decompensation bring them to the attention of the medical team to address. Signs to beware of include sudden weight gain (increase in weight by 2-3 pounds over night or 5 pounds over the course of a few days), increased cough or trouble laying flat or unusual increase in fatigue.
Research has found both strength and aerobic conditioning to be beneficial in individuals with CHF. Participation in regular exercise has shown to improve activity tolerance and functional capacity and can increase energy levels. Regular exercise improves circulation and electrical stability and reduces the risk of death from CHF. It is important, however, to keep in mind you should not participate in exercise if you ever find your CHF has become ‘uncompensated’ and if you have developed any signs of exacerbation. You should always report changes to medical team immediatly and hold off on activity until your condition is more stable.
The American Heart Association also has some great information about CHF here.
Or, you can watch a video about CHF here.
Valve Disorders
Lastly, issues can arise within the valves. While the valves between the atria, the ventricles and the veins and arteries are designed to be one-way, opening upon pressure and closing upon release, abnormal stress from CAD and hypertension can cause wear and tear. Leaving valve to remain open longer, blood may flow backward through the cardiac system instead of forward, causing increased risk of clotting and stroke. Valves can either become stenotic and narrowed and slow flow to and from the chambers, or incompetent and weak, allowing blood to flow back into the chamber it just left. Valve disease results in cardiac hypertrophy, placing the heart at increased risk of cardiomyopathy and resulting heart failure. While many cases of valve dysfunction may be asymptomatic, some may experience fatigue or dizziness, fainting or irregular heart beats. Your doctor may pick up on valve dysfunction during regular auscultation when they hear a murmur and this condition will need to be monitored and potentially addressed surgically if the case is severe. Keeping a heart-healthy diet, regularly taking any prescribed blood-pressure medications and participating in regular physical activity are all ways you can prevent heart valve disease.
The next area of potential problem is the Pulse. As introduced in the Basics, the cardiac cycle relies on the heart beat; the SA node fires first, communicating to the AV node, and the Purkinje fibers then pass along this message across the mycoardium to initiate contraction. When a problem occurs, somewhere along this network, you may develop arrhythmias, or irregular heart beats. While the type of arrhythmia varies depending on where the beat initiates, or where the message is dropped, Atrial Fibrillation is both common and problematic.
Atrial Fibrillation and other Arrhythmias
3-5% of individuals will develop A-Fib after the age of 65, and this rate doubles with each decade following. A-Fib develops when the message to contract becomes chaotic along the atrium and results in quivering instead of sustained contraction. Your heart rate will feel fast and light - upwards from 100-150 beats per minute. People often experience a sensation of fluttering in their chest, lightheadedness with activity and fatigue when they are in a period of atrial fibrillation. This can put you at an increased risk of stroke as this pattern may result in clot formation. Clots become problematic when they enter the bloodstream and travel towards the brain.
Individuals with A-fib are usually on a rate-regulating medication to keep their heart rate regular; when these meds fail, and a person enters A-fib that does not resolve on it’s own, they may have to enter the hospital for a cardioversion procedure. Some people will remain in A-fib for periods intermittently, and remain on a blood thinner ongoing to reduce their risk of stroke. While participation in exercise may not improve this condition specifically, it can improve the conditions that place you at risk of developing it. A-fib can develop from hypertension or CAD - the risk of developing these conditions can be mediated with exercise. It may also be triggered by hyperthyroidism or exposure to stimulants like caffeine, tobacco, alcohol or certain medications. Regardless, it is safe to work at light to moderate levels if you have diagnosed A-fib, which will benefit you in many other ways.
Other common arrhythmias include Premature Ventricular Contractions (or PVC’s) which are fairly common and benign, and the more ominous Ventricular Tachycardia which requires emergent medical attention. Regardless, becoming familiar with your heart rate, and being able to identify change, is a good way to stay on top of your heart health. You can watch this video here about how to assess your own heart rate.
Pacemakers and Implantable Cardioverter Defibrillators
Conditions like CHF with bundle branch block, sick sinus syndrome (aging-associated degeneration of the sinoatrial node), or patients that have survived sudden cardiac arrest or MI may be candidates for pacemaker or IACD implantation. These devices may be rate-responsive, biventricular pacers or AV pacers and may be combined with an implantable cardiac defibrillator (ICD). They all act to optimize normal heart rhythm and ensure maximum heart rate, stroke volume and cardiac output are all maintained in response to exercise and activity.
Lastly, we will take a look at the how problems in the Periphery can affect the heart. The heart relies on a system of vessels, veins and arteries, to carry blood to, then from, each of the organs, muscles, bones and tissues that perform all of your daily essential functions. Arteries are vessels that leave from the heart and they bring oxygen-rich blood to the periphery. Oxygen is extracted at their terminal destination for the purpose of energy production, then deoxygenated blood returns transfers back into the venous system for transport back to the heart. Ever wondered why your veins are blue? Oxygen-rich blood is red, due to the bound hemoglobin, while oxygen-poor blood is blue.
Hypertension
When problems develop along the periphery, slowing down the flow, it can also affect the heart function due to the increased strain this puts on the heart. Blockages or narrowing in the arterial system makes forces the heart to compensate by either pumping harder or pumping faster. Increasing the blood pressure, this compensatory cardiac reaction, places the the body in a state of hypertension, which is a precursor for all sorts of other heart conditions. However, and fortunately, hypertension something we can mitigate through lifestyle modification and exercise. The system becomes hypertensive either due to increased blood volume (cardiac output) or due to a problem with flow (increased peripheral resistance). When the system has too much volume, generally due to increased salt intake or kidney dysfunction, the heart has to work that much harder to pump it out each cycle. When the system develops problems with flow, the heart must work against higher resistance to pump the blood through vascular network. Atherosclerosis within the arterial system affects the flow. With atherosclerosis (the same atherosclerotic process that affects the cardiac arteries we talked about before), the arteries become harder and more narrow. High stress levels, releasing catecholamines, also increases the tone in the arteries, making the pathway tighter and more resistant to flow.
Peripheral Artery Disease (PAD)
When atherosclerosis develops in non-cardiac arteries, you can develop Peripheral Artery Disease. The reduction in peripheral blood flow can cause painful and intermittent cramping in the legs, buttocks and calf, though two thirds of individuals with PAD do not experience these symptoms. The pain associated intermittent claudication (IC) is triggered by activity, when active use makes the muscles demand more oxygen, and will then resolve with rest. While treated with the same medications as hypertension, more advanced disease may necessitate surgery to bypass the affected arteries. However, and the exciting thing (for me, at least) is that they’ve found that exercise CAN BE AS effective at improving this pain as surgical options. Progressive walking programs, designed to push slightly into pain, have been found to improve oxygen uptake in surrounding tissues and decrease vessel tone, and as such, can delay onset of IC pain and improve the experience of PAD-related symptoms.
Deep Vein Thrombosis and Pulmonary Embolism
Lastly, problems can occur along periphery when clots form and break loose. When a clot forms, but remains in place, this is called a Deep Vein Thrombosis, or DVT. When it breaks loose, and travels to the lungs, it is called a Pulmonary Embolism, or PE. Clots can also form and break loose and travel elsewhere, and if they make it to the brain, can cause a stroke, or to the heart, a heart attack. Fortunately, lifestyle modification can reduce your chances of developing these conditions. DVT risk is higher among smokers, in people who are sedentary and when you don’t follow your prescribed medication regimen. Many people at risk for DVT, either due to chronic A-fib or temporarily due to immobility after surgery, are put on a blood thinner. While some blood thinners are prescribed at a consistent dosage, others require ongoing monitoring of your clothing factor, or INR. These types of medications (usually coumadin) will require dosage adjustments depending on this value, and your doctor, INR clinic or nurse will help you determine what this daily dosage should be.
Prevention and Management of Cardiovascular Disease
Now that I’ve probably got your heart racing in fear (tachycardia, if you want another new fancy cardiac word to learn), I want to get to the important stuff.
You. Have. The. Power. To. Decrease. Your. Chances. Of. Developing. Scary. Heart. Conditions.
Did I say that clearly enough? Yes, these are not just things you have to live with because you are getting older. These are things you can control. Read on to part III in the HAE Cardiovascular series to learn more.
