Cardiology Flashcards
What is overdrive suppression?
The phenomenon where a period of excitation at high frequency depresses automaticity of pacemaker cells. The firing of the SA node tends to suppress the automaticity in the other loci because the SA node has a greater intrinsic rhythmicity than the other latent pacemaking sites in the heart.
What is automaticity?
It is the ability of the heart to initiate its own beat.
First degree AV block
An abnormal prolongation of AV conduction time. This slowed conduction normally takes places in the N region.
AV block
As the repetition rate of atrial depolarisation is increased, conduction through the AV junction slows. First (slowed), second (only a fraction of impulses propagated) and third (none of the atrial impulses conducted).
Second degree AV block
Conduction pattern in which only a fraction of the atrial impulses are conducted to the ventricles. This type of block may protect the ventricles from excessive contraction frequencies.
Third degree (or complete) AV block
Conduction pattern in which none of the atrial impulses reach the ventricles over a substantial number of atrial depolarisations. Third degree block is often associated with syncope (Stokes-Adams attacks).
AV node
Atrioventricular node. Divided into 3 functional regions. 1) the AN region, the transitional zone. 2) N region-middle portion. 3) NH region- zone in which nodal fibres gradually merge with the bundle of His.
What is normal QRS axis?
-30 degrees to +90 degrees. Predominantly positive QRS in leads I and II.
What is an ECG?
Electrocardiograph. A recording of the electrical activity of the heart from the skin.
How do you determine heart rate from an ECG?
1) 300 divided by the no. of large squares between each QRS complex.
2) No. of QRS complexes across ECG (10 seconds) x 6.
What is the normal QRS interval?
<3 small squares or <120ms.
What is the normal PR interval?
<1 large square or <200ms.
What is the normal QT interval?
<11 small squares or <440ms.
What is the major therapeutic use of adenosine?
An antiarrhythmic drug for the rapid treatment of supraventricular tachycardias. Its supression of atrioventricular conduction makes it very useful in treating paroxysmal supraventricular tachycardia in which the AV node is part of the reentry pathway (as in Wolff-Parkinson-White Syndrome). For these indications, adenosine is administered either as bolus intravenous injection or as an intravenous infusion.
What is a clinical trial?
An evaluation of a new therapeutic intervention (drug, device, procedure, surgery) in human volunteers.
Put the heart valves in order of most common site of infective endocarditis.
1) Mitral valve-most common site of infection.
2) Aortic
3) Tricupsid (most common site in IVDU)
4) Pulmonary valve-least common site of infection.
What is infective endocarditis?
Infection of the endocardium which is the lining of the heart, and this results in damage to the valve cusps.
What is Quorum Sensing?
The ability to detect and to respond to cell population density by gene regulation.
What are the HACEK organisms?
H-Haemophilus species. A-Aggregatibacter species. C-Cardiobacterium hominis. E-Eikenella corrodens K-Kingella.
What organisms cause endocarditis?
Both bacterial and fungal causes. Bacterial causes more common.
What are the 3 classifications of endocarditis?
1) Native valve endocarditis
2) Endocarditis in IVDUs
3) Prosthetic valve endocarditis
What is the most common cause of native valve endocarditis?
Streptococci, S. Viridans first followed by enterococci.
What is the most common cause of endocarditis in IVDUs?
Staphylococcus aureus.
What is the most common cause of endocarditis in prosthetic valve endocarditis?
Staphylococcus but more CoNS than S. aureus.
What are the risk factors for native valve endocarditis?
Underlying valve abnormalities in 55-75% of patients. Most common two: aortic stenosis and mitral valve prolapse.
What is rheumatic heart disease?
Rheumatic heart disease is cardiac inflammation and scarring triggered by an autoimmune reaction to infection with group A streptococci. In the acute stage, this condition consists of pancarditis, involving inflammation of the myocardium, endocardium, and epicardium. Chronic disease is manifested by valvular fibrosis, resulting in stenosis and/or insufficiency.
Early manifestations of IE
Fever and murmur=IE until proven otherwise.
What are the 2 hallmarks of embolic disease in IE?
Splinter haemorrhages and conjunctival petechiae.
How do you diagnose IE?
Blood culture and imaging. Blood culture-most important diagnostic, 3 bloods must be taken, must be done before giving antibiotics. Imaging is echocardiograph either transthoracic (non-invasive) or transopesophageal (invasive).
Define myocardial infarction
Any elevation of troponin in a clinical setting consistent with myocardial ischaemia. 5 different types.
CABG
A coronary artery bypass graft is a surgical procedure used to treat coronary heart disease. It diverts blood around narrowed or clogged parts of the major arteries to improve blood flow and oxygen supply to the heart.
Type 1 MI
Spontaneous MI due to primary coronary event (coronary artery plaque rupture and formation of thrombus).
Type 2 MI
Increased oxygen demand or decreased oxygen supply. Heart failure, sepsis, anaemia, arrhythmias, hypertension and hypotension.
Type 3 MI
Sudden cardiac death.
Type 4a MI
MI associated with percutaneous coronary intervention.
Type 4b MI
MI stent thrombosis documented by angiography or PM.
Type 5 MI
MI associated with CABG.
What are some chronic reasons for elevated troponin (not MI)?
- renal failure
- chronic heart failure
- infiltrative cardiomyopathies eg. amyloidosis, sarcoidosis, haemochromatosis.