Heart failure complications Flashcards
Examples of complications
- ruptured chordae tendinae (acute deterioration)
- intractable cough
- pulmonary hypertension
- pericardial effusion due to left atrial tear
- tussive syncope
- gross cardiomegaly
Function of the chordae tendinae
During atrial systole, blood flows from the atria to the ventricles down the pressure gradient. Chordae tendinae are relaxed as the AV valves are forced open.
When the ventricles contract in ventricular systole, increased blood pressures in both chambers push the AV valves to close simultaneously, preventing back flow of blood into the atria.
Since the bp in atria is much lower than the ventricles, the flaps attempt to evert to the low pressure regions.
The chordae tendinae prevent this prolapse by becoming tense, which pulls the flaps, holding them in closed position.
Ruptured chordae tendinae - presentation
Frequency present as an acute emergency, severe sudden LCHF
- severe dyspnoea
- stressed: panicking
- cyanotic
Is life threatening
Causes of worsening LCHF despite therapy
- worsening of dz (e.g. rupture of chordae tendinae, atrial tear)
- furosemide resistance?
- compliance?
- R sided failure & poor GI drug absorption?
What to do with worsening LCHF?
Changes to tx
- increase dose / frequency of furosemide
- increase dose / frequency of ACEi
- increase dose of pimobendan
Consider adding other drugs
- anti-dysrhythmic / negative chronotropes if tachydysrhythmic
- sildenafil if pulmonary hypertension
- an additional diuretic - thiazide/amiloride - often synergistic
Emergency CHF therapy for decompensation
Furosemide
- 2mg/kg IV initially then,
- 1mg/kg hourly afterwards under rr and effort reduce (up to 4 doses in cats, more as necessary in dogs)
Oxygen supplementation
Pimobendan
- consider injection
Cage rest
Avoid stress
Sedation as necessary (butorphanol 0.1-0.2mg/kg)
Monitor renal values / electrolytes
Anti-dysrhythmic meds if necessary
Pulmonary hypertension - causes
- Alveolar hypoxia with pulmonary vasoconstriction/remodelling
- severe resp dz e.g. IPF, neoplasia, etc - Pulmonary vascular obstructive dz
- pulmonary thromboembolism
- heart worm dz - pulmonary overcirculation
- large congenital shunts - high pulmonary venous pressure
- left sided heart failure of various causes can cause pulmonary hypertension - idiopathic
Left atrial tear - what happens? presentation? what not to do?
- acute bleed into the pericardium -> pericardial effusion
- can prevent with acute tamponade (R sided failure) and poor output
- avoid pericardiocentesis if possible as risk of moving clot
Tussive syncope - signalment? presentation? proposed mechanisms? tx?
- usually small breed dogs associated with chronic bronchitis / small airway dz, CDVD, BOAS, collapsing trachea
- syncope associated with coughing or occasionally with wretching/gagging etc
- 3 proposed mechanisms:
– increased intrathoracic pressure leading to reduced venous return
– decreased cerebral blood flow due to increased cerebral pressure
– tachyarrhythmias - treat underlying cause
– may need antitussive therapy
Intractable cough - what is it? causes?
= cough despite standard therapy
causes:
- unstable LCHF
- enlarged LA
- bronchomalacia -> large airway collapse
- co-existing chronic airway dz
re-radiograph?
if all else fails consider anti-tussive?
Cat cardiomyopathy complications?
- pleural effusion
- refractory heart failure
- thromboembolic dz
- sudden death
Pleural effusion - which cats? prevalence in dogs? types of effusion? why does it happen in left sided heart failure? theories?
- many cats with HCM present with a pleural effusion
- not so common in dogs
- modified transudate/chylous/pseudochylous
- backwards failure in LSHF -> congestion causes increased pressure in the pulmonary vein and therefore interstitial fluid leaks
- theories:
– pulmonary hypertension from LCHF causing right sided heart failure
– feline visceral pulmonary veins drain into the pulmonary veins
Thromboembolic dz - what is it a common complication of? onset of CS? what is it often mistaken for?
- common complication to HCM, RCM, FUCM (feline unclassified cardiomyopathy)
- often sudden onset of CS
- mistaken for neurological/traumatic dz
Thromboembolic dz - pathophysiology
Clot forms in atrium because:
- static blood
- endothelial damage
- cats blood is hypercoagulable
- Virchov’s triad satisfied
Thrombus lodges in terminal aorta - saddle thrombus - most common (>90% cats).
Some cats (<10%) thrombus in brachial artery / renal artery.
some cats thrombus in mitral valve - sudden death.
Feline arterial thromboembolism - presentation
- cold, cyanotic, paralysed hindlimbs
- absent femoral pulse
- hypothermia
- painful firm muscles
- vocalisation - vv painful
- ± dyspnoea due to CHF
- can present as sudden death
Feline arterial thromboembolism - diagnosis
- characteristic presentation
- acutely off back legs, v painful
- cardiac evaluation
- clinpath: renal function, muscle enzymes
- measure blood flow with Doppler
- US terminal aorta
Feline arterial thromboembolism - tx
- analgesics: opiates
- prevent further thrombus formation: aspirin, clopidogrel, LMWH
- treat CHF
- nursing care
- thrombolytic agents??
- amputation?
Feline arterial thromboembolism - prognosis
- repercussion injury: monitor potassium levels
- K ions are released once reperfusion occurs to damaged muscle
- metabolic acidosis and hyperkalaemia can be life threatening
- 1/3 survive, 1/3 die, 1/3 PTS
