Arrhythmias Flashcards
sinus bradycardia
originates in SA node
rate less than 60
sinus tacchycardia
originates in SA node
rate greater than 100
causes of sinus arrhythmias
resp: the P-P interval lengthens and shortens with inspiration and expiration
non-resp: where the process occurs seemingly for no reason
sometimes seen in association with complete heart block
Dilatation
the distension of an individual heart chamber
can be acute or chronic
hyptrophy
a chronic condition of the heart characterised by an increase in the thickness of a chamber’s myocardial wall
increase in its workload over time
Right atrial enlargement
usually caused by increased pressure and/or volume in the right atrium - right atrial overload
occurs in:
pulmonary valve stenosis, tricuspid valve stenosis and insufficiency, pulmonary hypertension from various causes
Left atrial enlargement
usually caused by an increased pressure and/or volume in the left atrium - left atrial overload
occurs in:
mitral valve stenosis and insufficiency, acute myocardial infarction, left heart failure, left ventricular hypertrophy
Right ventricular hypertrophy
caused by increase pressure in the right ventricle
occurs in: pulmonary valve stenosis, tricuspid valve insufficiency, pulmonary hypertension
ECG changes in right ventricular hypertrophy
QRS 0.12 secs or less
R waves: tall R waves in leads II and III and V1
S waves: relatively deeper than normal in lead I and V4-5
ST segments: downsloping ST depression in leads II, III, aVF and V1
T waves: T wave inversion in leads II, III, aVF, V1
left ventricular hypertrophy
caused by increased pressure in the left ventricle
occurs in: mitral insufficiency, aortic stenosis, systemic hypertension, MI, hypertophic cardiomyopathy
ECG changes in left ventricular hyptrophy
QRS 0.12 or less
slight QRS deviation to the left
R waves: tall in leads I and aVL and V5,6
S waves: deep S waves in lead III and V1,2
pericarditis
inflammatory disease of the pericardium, directly involving the epicardium with deposition of inflammatory cells and a variable amount of serous, fibrous, purulent or haemorrhagic exudate within the pericardial sac
causes of pericarditis
infectious agents acute MI trauma connective tissue diroders allergic and hypersensitivity disease metabolic disorders
Hyperkalaemia
excess of serum potassium above the normal levels of 3.5 to 5mEg/l
causes: kidney failure and certain duiretics
peaky T waves
Hypokalaemia
deficiency of serum potassium below the normal 3.5 to 5
common causes vomiting, gastric suction, excessive use of diuretics
hypercalaemia
excess serum calcium above the normal levels of 2.1 to 2.6
causes of hypercalcaemia
adrenal insufficiency hyperparathyroidism immobilisation kidney failure malignancy sarcoidosis thyrotoxicosis vitamin A and D intoxication
hypocalcaemia
shortage of serum calcium below the normal levels
causes of hypocalcaemia
chronic stetorrhea diuretics hypomagnesemia osteomalacis in adults and rickets in children hypoparathyroidism pregnancy resp alkalosis and hyperventilation
digitalis
administered within therapeutic range produces characteristic changes in the ECG
excitatory: premature atrial contractions, atrial tachycardia, nonparyoxysmal junctional tachy, premature ventricular contractions, ventricular tachy, ventricular fibrillation
inhibitory: sinus tachy, SA exit block, AV block
ECG characteristics of digitalis
PR intervals: prolonged over 0.20 seconds
ST segments: depressed in many leads
T waves: flattened, inverted, biphasic
QT intervals: shorter than normal for the HR
Patho of preexcitation syndromes
occurs when electrical impulses from the atria or AV junction into the ventricles through accessory conduction pathways
accessory conduction pathways are abnormal strands of myocardial fibers that conduct electrical impulses
can conduct impulses backwards
Accessory AV pathways (bundles of Kent)
accessory tracts responsible for WPW conduction
pathways conduct electrical impulses from atria to the ventricles, bypassing AV junction, producing premature depolarisation of ventricles
ECG changes: WPW
PR intervals shortened to less than 0.12
QRS greater than 0.12 seconds and abnormally shaped
Atrio-His fibers (James FIbers)
an accessory conduction pathway connects the atria with the lowermost part of the AV node, bypassing slower conducting AV node
ECG characteristics: Atrio-his fibers
PR intervals are usually shortened to less than 0.12
QRS normal
Nodoventricular/fasiculoventricular fibers (Mahaim fibers)
rare accessory conduction pathways provide bypass channels between the lower part of the AV node and the ventricles and the between the bundle of His and the ventricles
ECG characteristics of nodoventricular/fasiculoventricular fibers
PR intervals normal
QRS greater than 0.12 seconds adn abnormally shaped
Brugada Syndrome
pts presenting with ST segment elevation in leads V1-3, right branch block, suscpetibility to ventricular tachy arrhythmias
ECG changes: brugada syndrome
QRS complexes in V1-3 resemble a right bundle branch block without typical RR pattern
QT
Qt interval prolongation increases potential for lethal ventricular arrhythmias such as torsades
short QT are rare but when found are due to genetic disorders
Calculation for QT
QTc= QT (milliseconds) + 1.75 (ventricular rate - 60)
chronic cor pulmonale
enlargement of the right ventricle commonly accompanied by right heart failure
usually end stage result of prolonged pulmonary hypertension
early repolarisation
describes a form of myocardial repolarisation in which ST segment is elevated or depressed 1 to 3mm above or below the baseline respectively
Acute pulmonary embolism
occurs when a blood clot or other foreign matter lodges in a pulmonary artery and causes obstruction of blood flow to the lung segment supplied by the artery
hypothermia
causes a positive wave, the osborn wave
occurs at the junction of the QRS complex and ST segment
