Term
| prolonged P-R interval is consistent with what pathophysiologic abnormality in the heart? |
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Definition
slowed AV nodal conduction
*P wave = atrial depolarization
* R wave = ventricular depolarization |
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Term
| What ECG abnormality is consistent with first degree AV block? |
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Definition
prolonged P-R interval
*tends to be hemodynamicaly benign |
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Term
| What drugs can increase vagal tone and slow AV nodal conduction? What rhythm abnormality results? |
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Definition
| Opiods and digoxin can increase vagal tone and cause first degree AV block |
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Term
| What ECG abnormality is consistent with second degree AV block? |
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Definition
Non-propogated P waves
*AV nodal conduction is inhibited every couple of beats --> P wave w/out QRS
ratio of p waves : QRS complexes is usually 4:3 |
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Term
| T/F: Mobitz type I (aka Wenckeback phenomenon) is uncommon in small animals as is characterized by progressively lengthened P-R intervals leading up to the occurrence of a non-propogated P wave |
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Definition
TRUE
*common in horses, aka dropped beats |
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Term
| T/F: Mobitz type II is more common in dogs, and manifests as occasional second degree AV block with consistent P-R intervals leading up to the non-propogated P wave |
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Definition
TRUE
*often associated with premed drugs like oxymorphone (increases vagal tone) |
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Term
| T/F: second degree AV block can manifest as exercise intolerance |
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Definition
TRUE
associated with frequent non-propogated P-waves (5 p waves : 1 QRS complex) |
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Term
| What rhythm abnormality is characterized by P waves that are completely dissociated from QRS complexes? |
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Definition
3rd degree/complete AV block
*fibrosis/damage to the AV node junctional tissue results in pacemaker activity within AV/bundle/purkinje fibers independent of SA node rate |
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Term
| T/F: animals with 3rd degree AV block commonly present with tachycardias |
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Definition
FALSE
the impaired transmission through the AV node results in independent ventricular pacemaker activity - rate of ventricular pacemakers are ~40 (AV) to ~15-20 (bundle/purkinje) |
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Term
| T/F: medical therapy is the best treatment of 3rd degree AV block |
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Definition
FALSE
need to treat with a pacemaker |
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Term
| What ECG abnormalities and clinical signs are associated with sick sinus syndrome (esp. common in female schnauzers) |
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Definition
| long periods of asystole, presents clinically as regular episodes of syncope and is the manifestation of a global conduction system disorder |
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Term
| T/F: The best treatment for sick sinus syndrome (esp. in female schnauzers) is atropine |
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Definition
FALSE
periods of asystole in affected individuals are NOT the result of increased vagal tone, but rather a manifestation of global conduction system dysfunction -- TX with pacemaker |
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Term
| What arrhythmia is characterized by premature P waves followed by normal QRS complexes (i.e. shortened R-R interval)? |
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Definition
Supraventricular premature complex
*often associated with damaged atrial myocardium (ex. jet lesions) resulting in electrical instability and ectopic foci of depolarization |
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Term
| Tachycardia is defined as..... |
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Definition
| 3 or more premature complexes in sequence |
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Term
| Bigeminy is defined as...... |
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Definition
| one normal complex followed by one premature complex in a repetitive pattern |
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Term
| Trigeminy is defined as..... |
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Definition
two normal complexes followed by a single premature complex in a repetitive pattern
*not very common in domestic species |
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Term
| What rhythm abnormality is characterized by three or more early QRS complexes (normal morphology) in sequence? |
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Definition
paroxysmal supraventricular tachycardia
*p wave may be hard to see, but normal QRS morphology allows arrhythmia to be localized to the atria |
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Term
| T/F: the most consistent manifestation of atrial fibrillation on ECG is the presence of baseline undulations (F waves) |
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Definition
FALSE
F waves are unreliable in small animals and could be manifestations of motion artifact - still, their presence is supportive of atrial fibrilation |
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Term
| What arrythmia is characterized by absent/abnormal P waves, highly irregular R-R intervals, normal QRS complexes, and a fast rate? |
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Definition
atrial fibrillation
*common in sick animals, associated with significant atrial enlargement (potentially as a sequela to advanced heart disease) |
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Term
| What is the first line treatment for atrial fibrillation? |
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Definition
Digoxin
-increases vagal tone --> negative dromotrope (decreased rate of conduction through AV node) and negative chronotrope (decreased rate of conduction through SA node)
-positive inotrope (increases myocardial contractility) <-- this is good because many patients with atrial fibrillation have compromised contractility secondary to DCM
*note* digoxin only decreases heart rate, rhythm abnormality (ie. fibrillation) will NOT resolve |
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Term
| What other two classes of drugs can be used to treat atrial fibrillation of digoxin alone is not capable of lowering the heart rate below 160 bpm? |
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Definition
calcium channel blockers (*decreases contractility so DON'T use alone)
beta blockers |
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Term
| What rhythm abnormality is characterized by random wide bizarre biphasic QRS complexes occuring independent of a P wave? |
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Definition
ventricular premature complexes
*seldom necessary to tx the arrythmia but NEED to check for underlying disease |
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Term
| T/F: ventricular premature complexes are much more common than ventricular tachycardias |
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Definition
|
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Term
| What is the treatment of choice for ventricular tachycardia? |
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Definition
Lidocaine
*short duration of action so look for an underlying cause |
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Term
| What rhythm abnormality is characterized intermittent changes in heart rate with fusion beats at the transitions, and normal QRS complexes? |
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Definition
Accelerated idioventricular rhythm
*intermittent exchange between sinus and ventricular pacemakers, the ventricular rate is usually 10-20% higher than the sinus rate |
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Term
| T/F: accelerated idioventricular rhythm is the most common ventricular arrythmia (esp. in sick ICU patients) and is normally self limiting |
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Definition
TRUE
**additionally, AIR is completely unresponsive to medical tx so it's a good thing it's self limiting |
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Term
| what is the most common cause of left apical systolic murmur in dogs? |
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Definition
| degenerative valve disease |
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Term
| T/F: most patients with degenerative valve disease are asymptomatic and do not require treatment |
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Definition
TRUE
*may remain asymptomatic for years without therapy, may never develop CHF |
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Term
| What is the most important diagnostic test to r/in CHF? |
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Definition
Thoracic radiographs
*echo and ECG will NOT help dx CHF |
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Term
| What findings on thoracic radiographs are supportive of the the diagnosis of CHF? |
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Definition
large cardiac sillouette
caudodorsal interstitial to alveolar infiltrate (cardiogenic edema)
enlarged left atrium/auricle |
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Term
| What drug is the mainstay of CHF medical therapy? |
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Definition
furosemide
*life time therapy, PU/PD is the most commonly reported side effect |
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Term
| How does pimobendan help allieviate symptoms associated with CHF? |
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Definition
| positive ionotrope and vasodilator |
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Term
| Once initiating medical treatment of CHF (furosemide +/- enalapril +/- pimobendan) how frequently should you recheck serum chemistry and UA for azotemia and electrolyte imbalances? |
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Definition
| 1 week after starting treatment, then every 3 months |
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Term
| What is the most common congenital malformation in dogs? |
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Definition
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Term
| Why do PDA dogs present with a continuous murmur? |
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Definition
Aortic pressures are higher than pulmonary artery pressures in both systole and diastole
*murmur is best heard far cranial over the left heart base, can be very focal |
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Term
| What three radiographic findings are classically associated with PDA? |
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Definition
distended pulmonary artery, distended aorta, left auricular buldge
*best seen on VD, only present in 20% of cases |
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Term
| T/F: without treatment over half of dogs diagnosed with PDA will die within a year of initial Dx, usually of left sided CHF |
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Definition
TRUE
tx: surgical ligation or duct occluder device |
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Term
| Why is left ventricular hypertrophy a sequella to subaortic stenosis? |
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Definition
| Left ventricle must attain very high pressures to push blood through the narrow stenosis below the aortic valve, this results in hypertrophy as well as areas of fibrosis and electrical instability which can result in fatal arrhythmias |
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Term
| with congenital defect most commonly presents with a systolic murmur, loudest at aortic valve +/- weak pulses |
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Definition
subaortic stenosis
murmur is due to high velocity flow through the stenotic aortic valve --> increased turbulence and post stenotic dilation of the aorta |
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Term
| What is the normal outflow velocity into the aorta? |
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Definition
|
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Term
| T/F: the aorta and the left ventricle should have the same pressure |
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Definition
TRUE
*pressure gradients over 75 mmhg are associated with a poor prognosis (indicates that the left ventricular pressures are very high in order to achieve normal pressures in the aorta) |
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Term
| T/F: subaortic stenosis can progress in severity during the first 6-12 months of life, and affected animals should NOT be bred |
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Definition
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Term
| In patients with ventricular septal defects why is the murmur loudest over the tricuspid valve (ie. the right side)? |
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Definition
| higher pressure in the left ventricle reuslts in a L-R shunt--> jet of shunted blood impacts just in front of the tricuspid valve |
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Term
| What breed is most predisposed to tricuspid valve dysplasia? What abnormality is noted on ascultation? |
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Definition
Labs
murmur loudest on right hand side localized to the tricuspid valve |
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Term
| what is the most common sequela of tricuspid valve dysplasia? |
|
Definition
| enlarged right atrium --> atrial fibrilation and right sided CHF |
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Term
| Which congenital defect is most commonly associated with cyanosis? |
|
Definition
tetralogy of fallot
*pulmonic stenosis (due to atrestia) with secondary right ventricular hypertrophy, and large ventricular septal defect <-- lots of blood shunts through VSD and into the aorta bypassing the lungs --> cyanosis |
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Term
| What three abnormalities are present in tetralogy of fallot? |
|
Definition
Large ventricular septal deffect
pulmonic stenosis with secondary right ventricular hypertrophy |
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Term
| What congenital heart defect is more common in cats than dogs? |
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Definition
| Endocardial cushion deffect --> massive intra-atrial +/- ventricular septal defects |
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Term
| What is the treatment for tetrology of fallot? |
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Definition
| periodic phlebotomy (systemic hypoxia results in relative appropriate polycythemia), dogs can live up to 8-10 yrs |
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Term
| What ECG abnormalities are consistent with right atrial enlargement? |
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Definition
increased P wave amplitude
usually caused by pulmonary disease (ie. heartworm) |
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Term
| What ECG abnormalities are consistent with left atrial enlargement? |
|
Definition
prolonged duration of P wave
ex. mitral valve disease with regurgitation |
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Term
| What ECG abnormalities are consistent with right ventricular enlargement? |
|
Definition
Negative deflection of the R wave
ex. pulmonic stenosis, Heartworm disease |
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|
Term
| What ECG abnormalities are consistent with left ventricular enlargement? |
|
Definition
increased amplitude of R wave +/- prolonged duration of QRS complex
ex. volume overload associated with subaortic stenosis or DCM |
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Term
| T/F: evidence of bundle blocks on ECG necessitate aggressive medical therapy |
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Definition
FALSE
bundle blocks are usually hemodynamically benign |
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