Complete Heart Block, DVT, Fallots Tetralogy Flashcards
What occurs during complete heart block?
Complete failure of AV node (due to damage to AV node) to transmit electrical signals from atria to ventricles
Atria have electrical activity and contract independently of the ventricles which
develop their own pacemaker activity – usually at a much slower rate
What anatomical structure is affected during complete heart block?
AV node
What is normally physiology of electrical transmission in heart?
Transmission of electrical depolarisation wave from atria to ventricles
AV node induces a short delay in transmission – to allow atria to contract before ventricles contract
What is purpose of AV node inducing short delay?
Prevents both contracting together which would not allow tricuspid and mitral valves to open
What structural abnormalities of AV node are present in complete heart block?
- Fibrosis of AV node
- Necrosis / infarction of AV node
What is fibrosis of AV node?
Replacement of some of the normal cells with fibrous tissue due to cell death due to age
What is necrosis / infarction of AV node?
Death of all or most of cells as a result of coronary artery disease
Who is at risk of complete heart failure?
Elderly patient who may have had a prior myocardial infarction; be taking betablocker or other rate lowering drugs (digoxin, verapamil) that act to block AV node
How can complete heart block present?
- Gradually and in isolation (chronic complete heart block)
- Suddenly with other symptoms (acute)
What are symptoms of chronic complete heart block?
Tiredness and breathlessness with exercise
What are symptoms of acute complete heart block?
Light-headedness or
collapse with loss of consciousness
What is coronary artery disease?
Arteries that supply blood to heart muscle become hardened and narrowed due to build up of cholesterol and other material (atherosclerosis)
What are clinical signs of complete heart block relating to pulse/heart rate?
Pulse / heart rate – is slow (often much lower than 60 beats per minute)
What are clinical signs of complete heart block relating to blood pressure?
Often low
What may consciousness be like with patients with complete heart block?
Patient may be seen to suddenly lose consciousness for some seconds (called cardiac syncope)
What is medical/surgical intervention of complete heart block?
Ambulance / paramedic staff may administer atropine
A temporary pacemaker may be introduced immediately on arrival in hospital
What is purpose of atropine during complete heart block?
Blocks vagus nerve and acetyl
choline allowing the heart rate to rise
What does pacemaker do during complete heart block?
A wire is introduced into a vein and from there into the right ventricle – allowing a small
electrical impulse to be sent to stimulate the heart
Permanent pacemaker needed if complete heart block persists
What is DVT?
Blood clot forms in vein (thrombosis) located deep inside body (typically leg)
Usually first appears in calf (lower leg) but may extend above knee (femoral vein) and possibly into pelves (iliac veins) and abdomen (inferior vena cava)
What anatomical structures / physiology are affected by DVT?
Deep veins of leg (femoral and popliteal veins) and pelvis (iliac veins)
Return of deoxygenated block back to right side of heart (inferior vena cava) and then to the lungs (pulmonary artery)
How can DVT patients have hereditary thrombophilia?
Deficiencies in anticoagulation factors protein C, protein S, antithrombin, or mutations in the factor V and prothrombin genes
What is thrombophilia?
The tendency to develop thrombosis
How can recent surgery increase risk of DVT?
Blood vessels can be damaged in surgery which can lead to risk of clot.
Bed rest with little movement after surgery can lead to clot.
What else can contribute to risk of DVT?
Age, obesity, infection, immobilisation, combined (oestrogen-containing) contraception, tobacco, air travel
What do low-molecular-weight heparin (LMWH) treat?
Prevention of blood clots and treatment of DCT
What are symptoms for DVT?
- Swelling of right or left calf
- Pain in calf
- There may be no symptoms related to the leg – but sudden pulmonary embolus may occur
What are clinical signs of DVT?
- Swelling and redness of the leg and dilation of the surface veins
- Tenderness over veins when applying gentle pressure
- Physical examination is unreliable for excluding the diagnosis of deep vein
thrombosis
What would ultrasound of leg in DVT show?
Absence or reduction of venous flow and presence of thrombus within vein(s)
Why would D-dimer levels be tested for in low-probability situations of DVT?
This is a cross-linked fibrin
degradation product - an indication that thrombosis is occurring, and that the blood clot is being dissolved by plasmin
What is the immediate / 3 to 6 month treatment for DVT?
Immediate anticoagulation with low molecular weight heparin
3 to 6 month anticoagulation with Direct Oral Anticoagulant or Warfarin
Regular walking / exercise
What is fallots tetralogy?
A combination of four congenital abnormalities –> ventricular septal defect (VSD), pulmonary valve stenosis, a misplaced aorta and a thickened right ventricular wall (right ventricular hypertrophy)
What physiology is affected in fallots tetralogy?
Sequential flow of deoxy blood from right heart to lungs and oxy blood through left heart to body
What are the 4 structural abnormalities in fallots tetralogy?
- Ventricular Septal Defect (VSD) – a hole in the heart
- Pulmonary stenosis
- Overriding aorta
- Right ventricular hypertrophy
What is pulmonary stenosis?
A narrowing of pulmonary valve
What is overriding aorta?
Position is over right as well as left ventricle
What is right ventricular hypertrophy?
More muscular due to high pressure
How does fallots tetralogy result in low oxygenation of blood?
Mixing of oxygenated and deoxygenated in the left ventricle via the VSD
Why is there preferential flow of this mixed blood in fallots tetralogy through the aorta? What is this known as?
Because of obstruction to flow through the pulmonary valve and overriding aorta. This is known as a right-to-left shunt.
What are the prior events to fallots tetralogy?
Patients are born with this set of abnormalities with no recognisable prior events/causes
What is primary symptom of fallots tetralogy?
Low blood oxygen saturation with or without cyanosis (blue appearance due to low level of oxygen in arterial blood)
What are other symptoms of fallots tetralogy?
- From birth (congenital) or developing in the first year of life
- Difficulty in feeding
- Failure to gain weight
- Retarded growth and physical development
- Dyspnoea on exertion
What are the clinical signs of fallots tetralogy?
- Heart murmur which may range from almost imperceptible to very loud
- Clubbing of the fingers and toes
- Polycythaemia (excess of red blood cell)
- “Tet spells” characterized by a sudden, marked increase in cyanosis followed by syncope, and may result in hypoxic brain injury and death
- Older children will often squat during a “tet spell” which increases systemic
vascular resistance and allows for a temporary reversal of the shunt
What is cyanosis?
Blue tinged skin due to low level of oxygen in arterial blood
What would echocardiogram results be in fallots tetralogy?
Demonstrates abnormal anatomy and also a shunt of blood passing from left to right initially and later seen to shunt from right to left (Eisenmenger Complex)
What is an echocardiogram?
Ultrasound of heart
What is appearance of heart via chest x-ray in fallots tetralogy?
Abnormal ‘coeur-en-sabot’ (boot-like) appearance of heart
What is a ‘tet spell’?
Sometimes, babies who have tetralogy of Fallot will suddenly develop deep blue skin, nails and lips after crying or feeding, or when agitated. These episodes are called tet spells and are caused by a rapid drop in the amount of oxygen in the blood.
How are ‘tet spells’ treated?
Oxygen effective in treating ‘tet spells’
Why is oxygen effective at treating ‘tet spells’?
It is a potent pulmonary vasodilator and systemic vasoconstrictor which allows more blood flow to the lungs
What would surgery for early management of fallots tetralogy be for babies?
May involve forming an anastomosis (join) between the subclavian artery and the pulmonary artery to allow more blood to get to lungs
What is curative heart surgery used to relieve in fallots tetralogy?
Designed to relieve the right ventricular outflow tract stenosis by careful removal of muscle and repair of the VSD
Despite surgery – patients remain at increased risk of sudden cardiac death and heart failure
What is atropine?
Atropine is a medication used to treat certain types of nerve agent and pesticide poisonings as well as some types of slow heart rate and to decrease saliva production during surgery
How does acetyl choline affect heart rate?
Released by parasympathetic nerves at synapses with cardiac muscle cells. Binds to M2 muscarinic receptors, causing decrease in heart rate
What is cardiac syncope?
Suddenly lose consciousness for a few seconds
What is thrombophilia?
Thrombophilia (sometimes hypercoagulability or a prothrombotic state) is an abnormality of blood coagulation that increases the risk of thrombosis (blood clots in blood vessels)
