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
我们可以用赞叹的手臂拥抱一千条银河,但当那灿烂的光流贴近我们的前胸,最动人的音乐仍是一分钟六十次雄浑坚实如祭鼓的人类的心跳!
医生不是生命的创造者--他是协助生命神迹保持其本然秩序的人!