Temporary Cardiac Pacing

Dr. Md. Mashiul AlamPhase B resident

Chairperson: Prof. F. Rahman

Introduction

Temporary cardiac pacing involves electrical cardiac stimulation to treat a bradyarrhythmia or tachyarrhythmia until it resolves or until long-term therapy can be initiated.

The purpose of temporary pacing is to re-establish circulatory integrity and normal hemodynamics that are acutely compromised by a slow or fast heart rate.

Indication Acute hemodynamically significant bradycardia or

asystole Acute MI: New bifasicular block (RBBB + LAD or RAD) New LBBB with 1st degree AV block Alternating LBBB and RBBB Mobitz Type II and complete heart block ( in case of

hemodynamically significant in Inferior MI) RVI with loss of AV synchrony

Bridge to permanent pacing Termination of tachycardias (Overdrive pacing) Post cardiac surgery which may affect AV node

of His bundle Electrophysiological study Prophylactic during RHC in the setting LBBB Complex PCI in RCA Drug toxicity e.g., digoxin, beta blocker

Relative contraindication

• Poor vascular access• Bleeding disorder or anticoagulaiton therapy: INR should be > 1.8 Platelete count >50,000

Temporary pacing methods

• Transcutaneou ventricular pacing (TCP)• Transesophageal or transgastric pacing• Epicardial pacing• Transvenous pacing

TCP

Emergency treatment of sever bradycardia or asystole and bridge to transvenous pacing

Lead placement:• Anterior posterior position One at the anterior chest wall at V3 positon another one posteriorly below scapula• Anterior lateral position Over sternum and at apex

• Pulse width – 20 to 40 ms• High output – 100 to 200 mA

Common problem:Sever patient discomfortFailure to capture

Transesophageal or gastric pacing

• Flexible electrode on the tip of a catheter down the esophagus for atrial pacing

• Advanced to the fundus of stomach for ventricular pacing

Rarely used

Epicardial Pacing

At the time of aortic valve replacement, AV canal defect repair, tricuspid surgery or Ebstein anomaly correction

Epicardial pacing wires are placed in atrium and ventrical at the time of surgery. Fine small caliber wire are used only for a short period.

Transvenous pacing

• Patient preparaton: Infromed consent if possible ( no need in

emergency condition) Peripheral IV access if the procedure is elective should be performed in monitored setting

equipped with fluoroscopy and crash cart May be perfromed ECG or echo guided in some

situations

• SiteFemoral veinInternal jugular veinSubclavian veinBrachial vein

Ipsilateral subclavian vein should be avoided if permanent pacemaker is planned

Femoral approach is advisable if undergone thrombolysis

Temporary leads should be resited from femoral access sites after 48 hours and from other sites after 5-7 days when possible to prevent infection

• Lead choice- Active fixation leads allows greater pacemaker

stability Passive fixation lead – usually done

• Instruments C-arm image-intensifier/ fluroscope Temporary pacing box 5F temporary pacing wire 5F or 6F introducer sheath External pacemaker / defibrillator Cardiac monitor with non invasive / invasive

monitoring facilities Oxygen and air inlet

• Position of the patient: Supine in bed Tendelenberg postion for internal jugular and

subclavian approach for filling of the vein and prevention of air embolism

• Technique- Venous sheath is inserted by Seldinger

techniqueVentricular lead insertionAtrial lead insertion

Ventricular lead insertion

• Leads are straight or slightly angulated near the tip

• Pacing catheter is advanced through venous sheath under fluoroscopy guidance (20-30 degree LAO projection)

• Catheter advanced through tricuspid valve and turned either clockwise or anticlock wise to direct the tip anteriorly

• Attempt to cross TV directly• If unsuccessful gentle pressure applied with

catheter torqued to allow mid portion of catheter to prolapse across the valve or by looping the tip against the lateral atrial wall and rotating the loop medially

• Once catheter in the ventricle – it is rotated so that the tip points inferiorly to the apex

• The ideal catheter placement site- diaphragmatic surface or floor of the right ventricle anywhere between the midpoint and apex

• Placement at the Apex should be avoided as there is increased chance of perforation

• RVOT is a option but unstable tip location

Ensuring accurate lead placementTip will be located left side of the spine in AP

view and anterior inferior postion in lateral veiw. Some buckling is acceptable.

If tip is in coronary sinus the tip will be posterior superiorly directed in lateral view

• Leads are attached with the pulse generator….

Testing

Once catheter is in a stable position , threshold testing should be performed

Pacing rate: regulates the number of impulses that can be delivered to the heart per minute. The rate setting depends on the physiological needs of the patient.

Threshold: is the lowest energy, which will cause the myocardial cell to contract. The desired threshold is 0.5-1.0mA.

Sensing is the ability of the pacemaker to “see” when a natural (intrinsic) depolarization is occurring.– Pacemakers sense cardiac depolarization by measuring changes in electrical potential of myocardial cells between the anode and cathode.– Expressed in Millivolts (mV).

Setting stimulation threshold

• Set RATE at least 10 bpm above patient’s intrinsic rate.

• Decrease OUTPUT: Slowly turn OUTPUT dial counterclockwise until ECG

shows loss of capture.

• Increase OUTPUT: Slowly turn OUTPUT dial clockwise until ECG shows

consistent capture. This value is the stimulation threshold.

• Set OUTPUT to a value 2 to 3 times greater than the stimulation threshold

value.

• Restore RATE to previous value

.

Setting sensing threshold • Set rate at least 10 bpm below patient’s intrinsic rate.

• Adjust output: Set OUTPUT to 0.1 mA .

• Decrease SENSITIVITY: Slowly turn MENU PARAMETER dial counterclockwise until pace indicator flashes continuously.

• Increase SENSITIVITY: Slowly turn MENU PARAMETER dial clockwise until sense indicator flashes and pace indicator stops flashing. This value is the sensing threshold.

• Set SENSITIVITY to half (or less) the threshold value.

Post placement CXR

• To evaluate pneumothorax and proper position of lead after the procedure

Pacer Care

• Check catheter insertion site daily for signs of infection and apply regular sterile dressing at regular interval

• Obtain daily 12 lead surface ECG with and without pacing

• Check function daily by determining the sensing and pacing threshold and check underlying rhythm daily by decreasing the pacing rate gradually

Complication and troubleshooting

• Related to central venous access (Hematoma, Pneumothorax, hemothorax, air embolism, thrombosis, arterial puncture, AV fistula, infection)

• Cardiac arrythmia• Myocardial perforation echocardiogram should be performed Lead should be withdrawn only when there is all

facilities for percardiocentesis or surgical drainage

• CHB in a patent with prevous LBBB due to irritation of right bundle while lead placement

• Pacemaker relatedGenerator failure – change the generator/

keep an extra generator for emergencyVentricular non capture

Ventricular non capture/ capture failure

• Causes of Failure to Capture: Insufficient output Low pacemaker batteryDisplaced or fractured leadElectrolyte abnormalities: acidosis; hypoxia;

hypokalaemia

• Management: Increase output on Output dial lead may need to be repositioned or replacedCheck electrolytes View rhythm in different leads Change electrodes Check connections Change

battery, cables, pacemaker box

Ventricular undersensing

Potential for ventricula fibrilation ( due to R on T phenomena)

• Management: Increase sensitivity (reduce mV on Sense dial)lead may need to be repositioned or replacedView rhythm in different leads Change electrodes Check connections Change

cables, battery, pacemaker box Check electrolytes

Ventricular oversensing

Pacing does not occur when intrinsic rhythm is inadequate

• Pacemaker too sensitive • Possible lead displacement • Pacemaker failure

Danger of heart block, asystole

• Management: Reduce sensitivity (increase mV on Sense dial)lead may need to be repositioned or replacedView rhythm in different leadsChange electrodes Check connections Change cables, battery, pacemaker box Check

electrolytes

Thank you

There is no alternative to practical experience….