VHD and Shock

Valvular Disorders

Definitions 

• Stenosis = narrowing or “tightening”

• Regurgitation = insufficiency or “leaking”

• Types of disorders

  • Mitral Valve Stenosis

  • Mitral Valve Regurgitation

  • Aortic Valve Stenosis

  • Aortic Valve Regurgitation

Surgical Options to manage VHD

Balloon Valvuloplasty

• Commonly for mitral stenosis

  • Balloon is inflated to widen the narrowed mitral valve

• Requires pre-procedureal TEE to rule out thrombus formation

• Possibly for aortic stenosis if pt is too high-risk for cardiac surgery 
  
  

Valve Repair

• Fixing and preserving the pt’s native valve 

• Valve repair is preferred over replacement, if possible:

  • Lower operative mortality 

  • Better long-term outcomes

  • Preservation of left ventricular function

  • No anticoagulation 

Valve Replacement

Mechanical Valves	Bioprosthetic Valves
Types  1st Gen: Ball and Cage 2nd Gen: Single tilting disk  3rd Gen: Bileaflet tilting disk  Advantages High durability  Disadvantages Highly thrombogenic  Lifelong anticoagulation → if d/c it can cause clot Can have clicking sound	Types Porcine (pig) Bovine (cow) Advantages Less thrombogenic Disadvantages Low durability - will need replacement in 5-10 years More cardiac output → ↑ degradation (younger pts) Ideally for older pts
Preferred for young pts	Preferred for pts who have RF for bleeding or refuses or C/I to anticoagulation

Antithrombic Therapy for VHD

Mechanical	Bioprosthetic
Higher Thrombogenicity  Aortic Valve Warfarin w/ INR 2-3 indefinitely  Mitral Valve Warfarin w/ INR 2.5-3.5 indefinitely  Lower valve → higher clotting risk  Bridge w/ IV UFH or SC LMWH if INR subtherapeutic  Add aspirin 50-100mg/day if additional RF for thromboembolism AFIB Low EF Older age  History of TE ACC/AHA recommendation for INR 2.5-3.5 if pt has additional RF for thromboembolism (TE)	Lower thrombogenicity  Aortic Valve Aspirin 50-100 mg/day indefinitely  Optional: add clopidogrel 75mg QD for 3-6 months if transcatheter implantation (TAVI) Mitral Valve Warfarin w/ INR 2-3 for 3 months, then aspirin 50-100mg/day indefinitely

• Use of DOACs (dabigatran, rivaroxaban, apixaban, edoxaban)  are C/I w/ mechanical heart valves 

Pregnancy and VHD

• Bioprosthetic valve is preferred 

• Regimen for mechanical valve

  • Warfarin increases risk of congenital fetal abnormalities, fetal loss and hemorrhagic complications

    • If mother is willing, warfarin could be continued in 1st trimester if daily dose is <5 mg 

    • Most choose to use LMWH due to warfarin congenital effects

  • LMWH does not cross placenta 

    • BID SQ injections 

    • Must be monitored closely with anti-Xa levels

  • UFH IV LAST LINE 

  • Low dose aspirin added for high risk pts

Shock

• Shock: acute generalized state of inadequate perfusion of critical organs 

  • Defined as systolic BP <90 mmHg or reduction of at least 40 mmHg from baseline w/ perfusion abnormalities despite adequate fluid resuscitation

• Goals and Monitoring of Shock 

  • Goal is to achieve and maintain:

    • Mean arterial pressure (MAP) > 65 mmHg

    • Adequate perfusion to critical organs 

  • Global Monitoring 

    • Assesses perfusion and oxygenation of entire body 

    • Includes systemic BP, oxygen tension, lactate

  • Regional Monitoring 

    • Assess organ-specific oxygen delivery and utilization 

    • Ex: coagulation abnormalities, impaired renal or hepatic dysfunction, cool extremities, cardiac ischemia 

  
  
  

Management of Shock

	Cardiogenic	Obstructive	Hypovolemic	Distributive
Description	Heart fails to pump out blood	Heart pumps well, but outflow obstructed	Heart pumps well, but not enough blood volume to pump	Heart pumps well, but there is peripheral vasodilation
Examples of Etiology	Heart Failure,  Valve Dysfunction	Pulmonary Embolism,  Tamponade	Blood loss, Fluid loss	Anaphylaxis, Sepsis
Preload (Central Venous Pressure)	↑	↔	↓	↓
Afterload (Systemic Vascular Resistance)	↑	↑	↑	↓
Contractility (Cardiac Index, Stroke Volume)	↓	↓	↓	↑
General Treatment	Increase CO, Inotropes	Treat obstruction	IV fluids (crystalloids, colloids, blood)	IV fluids,  Vasopressors

Pharmacotherapy for Shock

Review of Receptor Physiology 

	A-1	B-1	B-2	DA	Vasopressin
Blood Vessels	Vasoconstriction		Vasodilation
Heart		Increased inotropy, chronotropy
Other			Bronchodilation	Vasodilation of kidneys	V1: Vasoconstriction V2: Reabsorption water in kidneys

Receptor Activity of Vasopressors

Drug	Dose	A	B-1	B-2	DA	Vasopressin
Dopamine  (ug/kg/min)	0.5-5		+		++++
	5-10	+	++		+++
	10-20	+++	++		+
Epinephrine (ug/kg/min)	0.01-0.05	+	+++	++
	>0.05	+++	++	++
Norepinephrine (ug/min)	0.5-30	++++	++
Phenylephrine (ug/min)	10-300	+++
Vasopressin (units/min)	0.01-0.06					+++

Vasopressors

	Administration	Receptors	Physiological Effects	Therapy
Epinephrine	IV push or titratable infusion	A1, B1, B2 agonist	→ Vasoconstriction → Increased inotropic / chronotropic	→ 1st line if pt is dead → Most common vasopressor used in life-threatening situations (cardiac arrest) → 3rd or 4th line in shock
Norepinephrine (Levophed)	IV as titratable infusion	Primarily A1, secondary B1 agonist	→ Vasoconstriction  → Increased inotropic / chronotropic	→ Preferred in sepsis, help with CO  → Most common vasopressor in ICU
Dopamine	IV as titratable infusion	Depends on dosing → High: D agonist → Med: B1 agonist → Low: A1 agonist	High: Vasoconstriction Med: Increased inotropic / chronotropic activity Low: Increased renal blood flow	→ Primarily used for cardiogenic shock
Phenylephrine (Neo-Synephrine)	IV as titratable infusion	A1 agonist	Vasoconstriction	Alternative vasopressor if tachyarrhythmias from norepinephrine or dopamine
Vasopressin	IV as titratable infusion  → also for diabetes insipidus		Vasoconstriction	Adjunctive therapy to norepinephrine in sepsis  → NOT MONOTHERAPY
AE	→ Arrhythmias → Tachycardia → Tissue ischemia (especially digit ischemia)