biventricular pacing

BIVENTRICULAR PACING

Zhu Yi ;Bai Lu; Jin Xingxing; Gu Hangyu;

Pan Lingxiao ;Li Ran

Agenda• Case Report• The Clinical Problem• Background Knowledge• Pathophysiology of LBBB• Operation of CRT• Mechanism of CRT• Clinical Uses of CRT• Adverse Effects• Combine with CCM

Case Report

• A 55-year-old man.• An anterior-wall myocardial infarction, 6 m ago.• Persistent shortness of breath with mild exertion, 3

m ago.• An exacerbation of congestive heart failure.• ECG: sinus rhythm, left bundle-branch block.• UCG: left ventricular ejection fraction of 25%.• Current treatment: furosemide, lisinopril, and

carvedilol.

• Further treatment: implantation of a biventricular pacemaker????

The Clinical Problem

• 1/4 ~ 1/3 heart failure have left bundle-branch block.

• Left bundle-branch block causes a poorer prognosis.

Background Knowledge

Regular cardiac output needs:

I. Electrical synchrony

II. Mechanical contractibility of cardiac muscle cells

How to achieve electrical synchronization?

I. Conductive pathway: sinus node internodal tract A-V node

bundle of His left and right bundle-branches Purkinje fiber

To assure:① Synchronization of left and right

ventricles② Coordination of atrium and

ventricles

II. Intercalated disc

Velocity of Conduction (m/

s)

SA node 0.1~0.2

Atrial 0.3~0.5

AV node 0.05~0.1

His Bundle 0.8~1.0

Purkinje Fibres* 2.0~5.0

Ventrcular* 0.3~0.5

Cardiac Conduction SystemCardiac Conduction System

Pathophysiology Of LBBB

• LBBB altered depolarization: Anterior septum inferior & lateral left wall

• Dyssynchronous contraction: Interventricular septum left free wall

• Inefficient contraction: Decrease of LVEF & CO

Cardiac Conduction System & Biventricular Pacing

Block of Conductive pathway leads to:

Ⅰ . Systole period: Synchronization↓ Strength↓ CO/CI↓ LVEF↓

Ⅱ . Diastole period: Coordination↓ A-V Filling Uncooperate Inadequate Blood Filling LVEF↓

Left Bundle Branch Block

• Organic Cardiopathy

• ECG：Sinus rhythm

Left deviation axis

QRS≥0.12s(Complete)

V1、 2 Leads：QS type

V5、 6 Leads： R type

ST-T Segment： Secondary Alteration

ECG Of Left Bundle Branch Block

Operation of CRT-----Pacemaker and Leads

Operation of CRT ---- Standard Approach of Leads

• Inserted pacing lead into mouth of the coronary sinus

• Advanced posteriorly around the atrioventricular-valve ring

• Passed into a venous branch running along the free wall of the left ventricle

Biventricular Pacing for CRT

Mechanism Of CRT

• Stimulate R & L ventricles; R atrium is also paced.

• Eliminate left wall delay.• Shorten QRS complex.• LV pressure rise rate↑ , pulse pressure↑

, stroke work↑ , CO/CI↑ , PCWP(LV function) ↓

• Not restore normal pattern.• Re-built a physiological mechanical pattern through

a fixed electrical pattern.

Effect Summary of CRT

• Improve ventricular function

• Not increase myocardial consumption

• Reverse ventricular remodeling

Clinical Use ---- Indications

• Dilated cardiomyopathy (ischemic or non-ischemic)

• LVEF ≤ 35%• QRS interval ≥ 120 msec• NYHA class III or IV despite optimal

medical therapy (Loop diuretics, BB, ACEI, ARB)

• Implantation of both CRT & CVD

Clinical Use -- Contraindications

• Increased risks of bleeding• Infection• Life-limiting medical condition• Heart failure requires parenteral

inotropic therapy

Adverse Effect -- Implantation

• Mutation-induced inability to implant LV lead

• Uncomfortable diaphragmatic stimulation – Hiccup

• Coronary-sinus dissection• Coronary-vein or -sinus perforation

– tamponade• Pneumothorax, complete heart

block, and asystole

Adverse Effect – Post-Op

• Dislodgment of the LV lead• Infection of the device

(Pacemaker pocket)• Atrial arrhythmias• External electromagnetic fields

interference (MRI, cell phone, power cable, electrical motor, electrocautery, radiation…)

Combine with CCM

I. CCM---- cardiac contraction modulating:

modulate Calcium current stimulate CMC in refractory period increase CMC contractibility directly

II. CRT---- cardiac resynchronization therapy:

assure synchronization

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