Mechanical Circulatory Support for the Advanced Practice Provider

Keyur B. Shah, M.D., F.A.C.C.

The Pauley Heart Center

Richmond , VA

Consultant: Medtronic

Research Grants: Thoratec/St.Jude/Abbott

I will not discuss off label use of medications or devices.

Disclosures

1. Determinants of LVAD Flow

2. Understanding LVAD Pulsatility

3. Some Basic points on clinical evaluation

4. Clinical Scenarios

Overview

Date 3Footer

What we are not covering

• History of devices

• Indications / Who to refer

• Outcomes

Determinants of LVAD Flow

What determines flow through an LVAD?

Flow Determinants

Flow (L/min)

Δ P

Δ P = “Pressure Differential”

Δ P = Aortic Pressure - LVEDP

Δ P = Afterload - Preload

Simplified Model

LVAD Flow during the Cardiac Cycle

• Components of the pressure differential are changing during the

cardiac cycle thus flow changes through the cardiac cycle

Δ P = Pressure at Outlet – Pressure at Inlet

Flow (L/min)

Δ

P

①

②

①

②

HMII Display Parameters

HVAD Monitor: Normal Waveform

Flow Determinants: LVAD Speed

Flow (L/min)

Δ P

Simplified Model

Impact of changing LVAD speed

Myers TJ. Annals of Thoracic Surgery. 2003

In a Simple World:

Parameter Change Examples Flow

Speed

↑

↓

Set by Clinician↑

Set by Clinician↓

Afterload

↑

↓

Vasopressors, HTN, outflow cannula kink

Vasodilators, Sepsis

↓

↑

Preload

↑

↓

Hypervolemia, AI

Bleeding, hypovolemia , RV failure, tamponade

↑

↓

All pumps are not the same!!

Flow (L/min)

Δ P

RED = HVAD ; WHITE = HMII

Key Points on So Far

• Flow through the LVAD has three

determinants

• Flow varies throughout the cardiac

cycle

Understanding “LVAD” Pulsatility

Pulsatility Index (PI)

• What is the PI:• Range 1-10

• measures magnitude of pulsatility

• Calculation of PI: • (Qmax – Qmin)/Qavg

• Avg Over 15 seconds

HVAD Display: Pulsatility

Beginning of systole

Beginning of diastole

Heart rate

Pulsatility

Waveform

Trough

Pulsatility Physiology Clinical Conditions

↑

Volume overload, improved RV function, pulmonary vasodilators

Inotropes, Recovery

Increase in Preload, Frank Starling Mechanism

Improved Myocardial Contractility

Decreased LVAD Speed

↓

Hypovolemia , RV failure, BleedDecreased Preload

Increased LVAD speed

Key Points so Far

• Flow through the LVAD has three determinants

• Flow varies throughout the cardiac cycle

• The Flow on the Monitor is estimated from power

• Pulsatility/PI Acute changes may be related to changed in LV Preload

Measuring Blood Pressure

Impact of changing LVAD speed

Myers TJ. Annals of Thoracic Surgery. 2003

Pulse

• Narrow pulse pressure with CF LVAD, often clinically undetectable

• Bounding pulse and symptoms of heart failure should be concerning for LVAD dysfunction

Myers TJ. Annals of Thoracic Surgery. 2003

Blood Pressure

• Can use automated cuff is patient is pulsatile

• Doppler to estimate the mean if pulse pressure is narrow (goal typically 70-90 mmHg)

Myers TJ. Annals of Thoracic Surgery. 2003

Now this…

Clinical Scenarios

Case 1.

PulsatilityOr PI

Physiology Clinical Conditions

↑

Volume overload, improved RV function, pulmonary vasodilators

Inotropes, Recovery

Increase in Preload, Frank Starling Mechanism

Improved Myocardial Contractility

Decreased LVAD Speed

↓

Decreased Preload

Increased LVAD speed

Hypertension

History

• 55 yo male

• 5 months s/p HVAD

• Symptoms: SOB with exertion

• Exam:

– BP: Doppler 105 mmHg; Cuff 105/90

– Regular rhythm, Faintly pulsatile, no edema

• ECHO: Poor systolic function, No MR, LV non

dilated, septum balanced

What to do?

Flow Determinants

Flow (L/min)

Δ P

Δ P = “Pressure Differential”

Δ P = Aortic Pressure - LVEDP

Δ P = Afterload - Preload

Simplified Model

Hypertension

Clinical CourseMAP = 88

mmHg

Case 2

• Patient post-op day 447

• LH, fatigued

• Exam

– MAP 75 mmHg

– Non pulsatile

– No edema

- Ecg: PVCs

Case 2

Lying Down

Standing up

Over-decompression of LV: Suction

• Differential

– Hypovolemia

– Right Ventricular Failure

– Poor RV function

– VERY high PVR

– Arrhythmia

– Too high LVAD speed

• 2 years s/p device implant, DT by choice

– edema and decreasing exercise tolerance

– continuous murmur over entire precordium

Case 3.

Pulsatility Physiology Clinical Conditions

↑

Volume overload, improved RV function, pulmonary vasodilators

Inotropes, Recovery

Increase in Preload, Frank Starling Mechanism

Improved Myocardial Contractility

Decreased LVAD Speed

↓

Hypovolemia , RV failure, BleedDecreased Preload

Increased LVAD speed

RHC

• RA 9 mmHg

• RV: 55/10

• PA: 55/ 28/37

• PAOP: 27

• C.O: 3.3 L/min\

• CI: 1.4 L/min/m2

Why low pulsatility on VAD monitor?

Changing Speed (all else constant)

Change Power Flow Pulsatility

↓ Speed ↓ ↓ ↑

↑ Speed ↑ ↑ ↓

Changing BP (all else constant)

Change Power Flow Pulsatility

↑BP ↓ ↓ ↑

↓BP ↑ ↑ ↓

Changing Volume

Change Power Flow Pulsatility

↓Preload ↓ ↓ ↓

↑Preload ↑ ↑ ↑