Information for Physiotherapists
1. Anatomy of the heart
The heart consists of involuntary muscle tissue (myocardium), which is lined by the endocardium and covered by the pericardium. It contracts and relaxes rhythmically in order to pump oxygenated blood throughout the body.
The heart consists of 4 chambers:
Right Atrium (RA), receiving venous blood from the Superior and Inferior Vena Cava.
Right Ventricle (RV), receiving blood from RA via the Tricuspid valve during ventricular diastole, and expelling blood to the Pulmonary artery via the Pulmonary valve during ventricular systole.
Left Atrium (LA), receiving oxygenated blood from the Pulmonary vein.
Left Ventricle (LV), receiving blood from the Left Atrium via the Mitral valve, and expelling blood to the Aorta through the Aortic valve during ventricular systole. This chamber is the biggest of the 4 and has the thickest muscle.
The 2 atrial chambers are separated by the Atrial Septum, and the ventricles are separated by the Ventricular Septum.
The Sinoatrial node (SA node) is located in the RA wall and acts as the natural pacemaker of the heart. This specialised tissue consists of numerous autonomic nerve endings with parasympathetic fibers, derived from the right Vagus nerve. It contracts by itself more or less 72 times per minute.
The impulse spreads from the SA node via the Perkunje fibers over the atria, to the Atrioventricular node (AV node). Here the impulse is slowed down, giving the atria time to contract fully and expel their contents to the ventricles before the ventricles start contracting. The impulse is then carried over the ventricles, causing them to contract.
The heart receives its own blood supply from 2 main arteries, each with 2 main branches. The Right Coronary Artery branches off the Aorta, and forms its own 2 branches, the Marginal branch and the Posterior Descending Coronary Artery.
The Left Coronary Artery (Left Main Stem Artery) also branches off the Aorta, and forms the Circumflex Artery and the Left Anterior Descending Artery.
The coronary veins do not empty into a larger vein, but empties directly into the right atrium.
2. What can go wrong?
· Valvular stenosis may be caused by rheumatic fever, causing the opening to be too small for blood to move effortlessly.
· Valvular regurgitation. Valves are worn, not closing properly, causing blood to dam up behind the valve. This reduces the stroke volume significantly.
· Atrial/Ventricular septal defects. This is often referred to as having ‘a hole in the heart.’
· Coronary Artery Disease (CAD). Atherosclerosis causing narrowing of the coronary arteries. If the heart muscle does not receive enough oxygen, it will lead to angina and eventual myocardial infarct (MI) if the circulation is not restored in time. During an MI part of the myocardium dies.
· Aneurysm – weak area in the artery, causing a bulge that may rupture.
· Congestive Heart Failure (CHF) is a condition that occurs when the heart does not pump enough blood to provide in the needs of the body. It is unable to pump out all the blood in the chambers. It may occur as a direct result of CAD, damage after an MI, diabetes, cardiomyopathies, high blood pressure or valvular heart disease, or it may occur over time as the heart tries to compensate for abnormalities such as the ones mentioned.
Patients with left-sided heart failure have symptoms of fatigue and dyspnoea, caused by fluid in the lungs.
Patients with right-sided heart failure also complain of fatigue and have oedema of the feet and ankles, as the venous return to the heart slows down.
CHF is a major cause of arrhythmias.
· Arrhythmia is the change in the normal beat of the heart. The heart may skip a beat, or beat very fast or very slow. May be caused by heart disease, or by caffeine, alcohol, diet pills, stress, cough/cold medicines. Sinus Arrhythmia is the most common.
· Infection or inflammation of the heart (cardiomyopathy and cardiomylitis).
3. What can be done?
Drugs containing nitric oxide are helpful in relaxing the muscles in the blood vessels (nitroglycerine being the most common).
Beta-blockers decrease the demand for oxygen of the heart by slowing the heart rate down and decreasing the pressure.
Anti-clotting agents are used to treat unstable angina and prevent blood clotting during surgeries (Warfarin being the most common).
Drugs may also be administered to reduce cholesterol.
Percutaneous coronary intervention (PCI) may be performed during the diagnostic angiography procedure. A tiny catheter is inserted into the heart vessels via the Femoral or Brachial arteries. A small balloon connected to the catheter is blown up inside the stenosed vessel in order to stretch it, for the blood to be able to pass through with more ease. A small tube may also be inserted into the artery, pushing its walls apart to keep it open. This is called stenting. Both these techniques are used for patients with CAD.
Coronary Artery Bypass Grafting (CABG) is an operation during which the surgeon uses a vessel (usually the Greater Saphenous Vein, Left or Right Internal Mammary Arteries) harvested from the patient, to replace the coronary artery that was occluded. A sternotomy is done. This is indicated for patients with CAD, and may be done on or off cardiopulmonary bypass (CPB). Patients on CPB do not have any blood pumping through their hearts during the operation. Instead, the blood goes through an external circuit (collecting the blood from the Superior and Inferior Vena Cava), which filters and oxygenates the blood before it is returned to the Aorta.
Valve Replacements are also done via sternotomy. Artificial (prosthetic) valves, bioprosthesis (tissue graft) or Allograft (preserved human valve) may be used.
Valve Repairs (Valvoplasty) and Septal defect repairs are also done via sternotomy.
Atrial septal defect (ASD) and Ventricular septal defect (VSD) repairs are done.
Heart transplants are indicated for patients with CHF, not responding well to drug treatment.
Pacemakers and defibrillators
Are used in the treatment of arrhythmias not responding to drug therapy.
4. Post-operative medical management
The post-operative management objective is to maintain a cardiac output that is adequate for tissue perfusion.
· Cardiac output: Cardiac output is assessed directly or indirectly from evidence of perfusion of brain (cerebral function), kidneys (hourly urine output) and feet (warm, filled veins, palpable arterial pulses).
Cardiac output = stroke volume x heart rate. The stroke volume is adjusted by altering the filling pressures and myocardial contractility. The heart rate is maintained by drugs or a pacemaker.
If the cardiac output remains low, the afterload of the LV may be reduced with vasodilators and reducing the body’s oxygen consumption minimizes the effects of poor tissue perfusion.
· Filling pressures of ventricles (Preload): The filling pressure (arterial pressure) of the ventricle most under stress is raised by transfusion until the cardiac output is judged to be normal. Further transfusion only causes pulmonary venous congestion and systemic venous congestion. A LA pressure of 25 mmHg is the maximum which can be sustained without pulmonary oedema.
· Myocardial contractility: If the cardiac output is still inadequate with optimal filling pressures, myocardial contractility can be improved by an inotrope. Metabolic acidosis, which depresses contractility is corrected by sodium bicarbonate. Arterial blood oxygenation is maintained by keeping the lungs clear of secretions and atelectasis.
· Heart rate: The heart is kept at 80 – 100/min (can use pacing wires). Arrhythmias are treated with drugs or DC shock (cardioversion) if interfering with function.
· Reduce afterload: The peripheral resistance (afterload) is reduced with vasodilators.
· Prevent effects of reduced cardiac output on other organs: Maintaining kidney output – kidneys tolerate ischaemia better if they are producing urine.
Reducing the oxygen consumption of the body by sedating the patient, intermittent positive pressure ventilation (IPPV), using muscle relaxants if necessary.
5. Post-operative complications of cardiac surgery
· Low cardiac output syndrome (LCOS): Restless, cold, venoconstricted extremities, peripheral cyanosis, sinus tachycardia, low urine output, low oxygen saturation and metabolic acidosis suggest that the cardiac output is low.
· Haemorrhage: Due to inadequate surgical haematosis or decreased capacity of the blood to coagulate. In addition to the signs of LCOS, the patient is pale and sweating, breathing rapidly with a low venous pressure.
· Tamponade: Haemorrhage into the pericardium, preventing filling of the ventricles. Treatment: immediate re-exploration.
· Cardiac failure: May occur due to myocardial damage during surgery. Severe ventricular dysfunction causes LCOS and is treated by adjusting the filling pressure of the ventricles, inotropes (to improve contractility), vasodilators (to decrease afterload) and removing the work of respiration by IPPV.
If these measures fail, left ventricular dysfunction may be relieved by an intra-aortic balloon pump (IABP). The balloon is inflated during systole, and deflated during diastole, improving blood pressure and coronary blood flow. (The IABP is inserted via the Femoral Artery – the hip should not be flexed during treatment.)
· Pulmonary hypertension: CPB often raises further the pulmonary vascular resistance in patients with pre-operative pulmonary hypertension. Vasodilators and inotropic support for the right ventricle are used.
· Arrhythmias: Tachycardias arising from either the atria or ventricles can compromise cardiac output and may need drug treatment or cardioversion (shock treatment).
Severe bradycardias are best treated by atrial or ventricular pacing via temporary epicardial wires.
· Renal failure: Oliguria following cardiac surgery is usually due to tubular necrosis caused by a low renal blood flow. Blood urea and serum potassium rise. Conservative measures involve fluid restriction and ion exchange resins; if this fails haemodialysis is used.
· Cerebral damage: Due to anoxia or embolism of air, thrombus, calcium, fat or silicone. It is treated by maintaining a normal blood pressure, decreasing carbon dioxide tension, avoiding hyperpyrexia and giving steroids as necessary.
· Respiratory failure: Respiratory complications are common following CPB which increases lung water, promoting patchy atelectasis and hence V/Q (Ventilation/Perfusion) mismatch and hypoxia. Diuretics and optimizing cardiac output improves lung compliance. Effective physical therapy is essential.
Rehabilitation of the Cardiac Patient
Clinical indications and contraindications for inpatient and outpatient cardiac rehabilitation:
- Medically stable post-MI
- Stable angina
- Coronary artery bypass graft (CABG) surgery
- Percutaneous transluminal coronary angioplasty (PTCA)
- Compensative congestive heart failure (CHF)
- Heart or other organ transplantation
- Other cardiac surgery including valvular and pacemaker insertion
- Peripheral vascular disease (PVD)
- High-risk cardiovascular disease ineligible for surgical intervention
- Sudden cardiac death syndrome
- End-stage renal disease
- At risk for CAD, with diagnosis of diabetes mellitus, hyperlipidemia, hypertension, etc.
- Other patients who may benefit from structured exercise and/or patient education (based on physician referral and consensus of the rehabilitation team)
- Unstable angina
- Resting SBP >200mmHg or resting DBP >110mmHg should be evaluated on a case-by-case basis
- Orthostatic BP drop of > 20mmHg, with symptoms
- Critical aortic stenosis (peak systolic pressure gradient > 50mmHg with aortic valve orifice area <>2 in average size adult)
- Acute systemic illness or fever
- Uncontrolled atrial or ventricular arrhythmias
- Uncontrolled sinus tachycardia ( > 120 beats/min)
- Uncompensated CHF
- Third degree AV block (without pacemaker)
- Active pericarditis or myocarditis
- Recent embolism
- Uncontrolled diabetes (resting blood glucose > 15 – 20 mmol/L)
- Severe orthopedic problems that would prohibit exercise
- Other metabolic problems, such as acute thyroiditis, hypo- or hyperkalemia, hypovolaemia, etc. (Kenney. 1995: 179)
Physiotherapy and the Cardiac Surgical Patient
NB: This is to serve as a guideline only. Each case should be assessed individually and progression should take place at each patient’s own pace.
The Physiotherapist (PT) should assess the patient before surgery and explain the rehabilitation program and precautionary measures post-surgery.
The following information should be obtained:
- Reason for admission/referral
- Medical history – Previous MI/TIA/stroke/surgery etc.
- Current symptoms – angina, palpitations, SOB, claudication etc.
- Current medication
- Social history – Does he live alone? House with stairs? What type of job does he do? Does he smoke – how many and how long for?
- Physical ability – how far can the patient walk before he feels SOB? Can he climb stairs? Does he have any physical handicap etc.
- Vital signs
- Inspection of LE for oedema, Dorsalis Pedis pulse, perfusion.
During the pre-op visit, the patient should be informed about the first stage of rehabilitation – that he will be helped to sit in a chair and walk a short distance on the first day after the operation, if all goes well. He will have to walk a bit further every day, and should be able to climb stairs, eat, drink and dress himself without major difficulty or discomfort prior to discharge (usually after 5 – 7 days).
The patient should also be made aware of the precautions that need to be taken for 6 weeks after surgery:
Due to the sternotomy, the patient will not be allowed to push on his hands or elbows, or be pulled on his arms. This may cause movement in the sternal bone and may interfere with the healing process. The therapist should show the patient how to stand up from sitting, sit up from lying down (with help) and how to ‘bum shuffle’ back into a chair. They should ‘hug’ their chests during coughing to support the wound.
The patient will have to wear pressure stockings for 6 weeks after the operation, to decrease the risk of DVT. The stockings should be worn at all times.
The patient will also not be allowed to lift anything heavier than 2 – 3 lbs for 6 weeks after the operation.
Patients are usually rather anxious prior to heart surgery. It is important to orientate them to the program, let them know what they can expect in ICU, and inform them about the drains and lines that will be attached for a day or 2: the Central line (usually subclavian), Arterial line (usually Brachial), chest drain which causes discomfort on coughing and movement, urinary catheter and monitoring cables.
Phase 1: Post-op till discharge
As soon as the patient’s condition is stable, he should be mobilized to a chair. This usually takes place during the morning or early afternoon, the first day post-op. The patient should sit in the chair as tolerated – nausea and dizziness are common at this stage, but aim for 1 – 2 hours. If the dizziness does not disappear, it may be due to low Hb, and the patient may need a blood transfusion.
Light shoulder exercises may be done if pain permits. NB: NO pushing/pulling on arms, no lifting of objects over 2 – 3 lbs, no horizontal extension of arms.
The patient will have a central line, arterial line, urine catheter, chest drain (connected to vacuum), pressure stockings, oxygen and monitoring cables attached. If the patient is stable, the monitoring cables may be removed and vacuum disconnected during the transfer. All drains should be clamped when lifted or passed over the bed.
The patient should rest for a few hours in the afternoon before he is to get up again and take a short walk. Mobile oxygen supply may be necessary.
It is very important to monitor all vital signs throughout treatment. BP should not change by more than 20mmHg (SBP or DBP), heart rate should not increase more than 20 – 25 bpm, oxygen saturation should stay above 95% (this may be influenced by lung disease) and the patient should never be too short of breath to hold a conversation. Vital signs before and after treatment should be documented.
From the second day post-op the patient should increase the distance walked, aiming to walk 15 – 20 minutes (usually by the third or fourth day post-op) twice per day. The pace should be comfortable – as soon as the patient becomes too SOB to hold a conversation, he is working too hard and needs to rest before carrying on. On the other hand, if the patient if the patient is able to sing, he should walk a bit faster.
By the third or fourth day the patient should attempt stair climbing. For many patients this is a milestone, and worth performing before discharge as many of them will have to climb stairs at home. Stair climbing should be incorporated into the daily walking regime.
Once the patient goes home, he should be aware of the importance of building the heart’s stamina levels and should be motivated to follow a specific walking program. The guidelines are set out in the hand-out (attached) that each patient receives prior to discharge. If the patient will not return to the Physical Medicine Department for Phase 2 – 4 of the rehabilitation program, he should continue with the program at home. If the patient is motivated and reliable, it may be a good idea to teach him to take his own pulse and exercise in the target heart rate (THR) range. Initially the THR is 20 beats more than the resting heart rate. After 2 weeks, the patient may calculate his THR as follows:
Maximum Heart Rate (MHR) = 220 – age
THR is between 60% and 80% of the MHR
Example: A 50 year old man has a THR of: 220 – 50 = 170
60% of 170 is 102
80% of 170 is 136
This man has to work at a pace that will keep his heart rate between 102 and 136 for optimal benefit.
The patient should be aware that any angina type chest pain, severe SOB, palpitations or a feeling that your heart is racing away for more than 5 minutes, are danger signs and the patient should stop exercising immediately.
Phase 2: Discharge – 6 weeks post-op
During this phase the patient should attend as an out-patient. Exercise sessions should take place a minimum of 3 times per week, and should progress from 10 min – 60 min as the patient’s functional capacity and clinical status improves. The exercise time should increase to 20 – 30 minutes before the intensity is to be increased. THR should be maintained for half of the exercise time. The exercise regime should incorporate warm-up, cardiovascular conditioning, shoulder mobilizations and cool-down.
Phase 3: From 6 weeks post-op
The patient may start with lifting weights after 6 weeks, if the surgeon agrees that the sternum is stable. This should be incorporated into the rehabilitation plan.
At this stage the patient should have a stable resting heart rate of below 90, and resting BP of below 140/90.
Intensity and length of exercise session should increase.
Phase 4: Maintenance program: Approx 6 months after hospital discharge
This stage is important to maintain fitness levels and incorporate sport/activity-specific exercises.