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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.
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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: • Electrical synchrony • Mechanical contractibility of cardiac muscle cells
How to achieve electrical synchronization? • Conductive pathway: sinus node internodal tract A-V node bundle of His left and right bundle-branches Purkinje fiber To assure: • Synchronization of left and right ventricles • Coordination of atrium and ventricles II. Intercalated disc
Cardiac Conduction System Velocity of Conduction (m/s) SA node 0.1~0.2 Atrial 0.3~0.5 AV node0.05~0.1 His Bundle 0.8~1.0 Purkinje Fibres*2.0~5.0 Ventrcular*0.3~0.5
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
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
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
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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