cvr arrythmias Flashcards
what is excitation contration coupling?
an electrical impulse that causes myocytes to contract via clacium induced calcium release.
dromotropy?
cardiac electrical conduting fibres responsible
bachmann’s bundle?
In the heart’s conduction system, Bachmann’s bundle, or the interatrial tract, is a branch of the anterior internodal tract that resides on the inner wall of the left atrium. It is a broad band of cardiac muscle that passes from the right atrium, between the superior vena cava and the ascending aorta.[1] Bachmann’s bundle is, during normal sinus rhythm, the preferential path for electrical activation of the left atrium. It is therefore considered to be part of the “atrial conduction system” of the heart.
volage gated ion channels
responsible for dromotropy
conduction phases?
0 - rapid depolarisation of membrane (influx of cations -mostrly Na+)
1- partial repolarisation as the inactivation threshold for Na+ channels is reached
phase 2 ‘plateau’ - caused by slow influxing Ca2+ traffic and some K+ inward currrents
3 - rapid and full membrane repolarisaion as Ca2+ challens inactivate and K+ traffics out of cells
4 ‘pacemaker’ - gradual influx of caions (Ca2+) which creeps up oitential until AP threshold is reached again.
ectopic beats
damage or patholog ca cause sustained partial depolarisation to mycardial tissue that would not normally exhibit pacemaker activity
plus:
catecholamines (e.g. adrenaline) increase the slope of phase 4 and can cause quiescent cells to generate spontaeous rhythm
Ectopic beat (or cardiac ectopy) is a disturbance of the cardiac rhythm frequently related to the electrical conduction system of the heart, in which beats arise from fiber or group of fibers outside the region in the heart muscle ordinarily responsible for impulse formation, i.e., the Sinus node.[1] Depending upon the origins of the ectopic beat within the myocardium, an ectopic beat can be further classified as either a premature ventricular contraction or a premature atrial contraction. Some patients describe this experience as a 'flip' or a 'jolt' in the chest, while others report dropped or missed beats. Such extrasystoles are more common during periods of stress or debility; they may also be triggered by consumption of some food like alcohol, strong cheese or chocolates, etc. It is a form of cardiac arrhythmia in which ectopic foci within either ventricular or atrial myocardium, or from finer branches of the electric transduction system, cause additional beats of the heart. Some medications may worsen the condition.
drug that cause DAD?
digoxin
adrenaline
some phosphodiestrerase inhibitors
conduction pahe pic
dispyramide?
used for - ventricular tachycardias particularly afer MI, suprventricular tachycardias
mech - blocks alpha subunit of Na+ channels, prolongs AP. intermediate release
Dose - 300-800 mg, slow i.v. 2mg/kg over 5 mins to max of 150 mg with monitoring
ADR - torsade de pointes, QT elongation, ventricular arrythmias, anti-muscarinic effects
contra-indications: - heart block, cardiogenic shock, uncompensated heart failure, acute porphyria
lignocaine
used for - ventricular tachycardias particularly afer MI, suprventricular tachycardias
mech - blocks alpha subunit of Na+ channels, prolongs AP . fast speed of dissociation from channel
Dose - iv bolus 100mg over 5 mins then 4mg/min infuction for 30 mins, titring down with ECG monitoring
ADR - bradycardia, drowsiness, parasthesia
contra-indications: - all grades of arioventricular block. acute porphyria
flecainide
used for - AV node reciprocating tachycardia, WPW, AF, sustained VT
mech - blocks alpha subunit of Na+ channels, prolongs AP. slow speed of dissociation form channel
Dose - p.o. Ventricular arrythmias 100mg BDS
p.o. (SVT) 50mg BDA. slow i.v. 2mg/kg for 0 mins with ECG monitoring
ADR - oedema, CNS distrubances, cardiac arythmias
contra-indications: - pacemakers, AF following surgery
atenolol?
used for - aniety, tachycardia, SVT, VT, hypertension, angina
mech - reduce slope of phase 4 in cardia AP
Dose - p.o. 50-110 mg daily, i.v. 2.5mg @ 1mg/min in 5 min intervals to a maximum of 10mg
ADR - bradycardia, hypotensioin, bronchospams, heart failure, sexual dysfunction
contra-indications: -asthma, heart block, heart failure, do not use woith veraamil (asystole), hypotension
bisoprolol>
used for - aniety, tachycardia, SVT, VT, hypertension, angina
mech - reduce slope of phase 4 in cardia AP
Dose - hyperntension/angina p.p. 10mg OD
heart failure - initially p.o. 1.25mg OD, with monitoing
ADR - bradycardia, hypotensioin, bronchospams, heart failure, sexual dysfunction
contra-indications: -asthma, do not use woith veraamil (asystole), hypotension
amiodorone
verapamil
diltiazem?
amlodipine?
adenosine?
digoxin?
adrenaline?
atropine
