الفهرس 
Physiological ReviewOnly 14 pages are availabe for public view
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Abstract
As the need for mechanical circulatory assistance : increasing,
advances and development in its structure, function, and COl rol continue
to influence the outcome and the patient benefit. Howeve the devices
available today are the result of long and hard we k by many
investigators, researchers, and clinicians.
Despite substantial improvement in myocardial p otection and
other technical advances, postoperative ventricular dysfunct on persists as
a complication in 2-6% of all patients undergoing cardii : or thoracic
aortic sugary. Despite maximal inotropic therapy, 0.5- % of these
patients can not be weaned readily from CPB and would require some
form of mechanical cardiac assistance to achieve adeq ate systemic
pressure and perfusion.
The currently available circulatory assist devices ar the artificial
cardiac pacemaker, the intraaortic balloon pump, the vel ricular assist
devices, and the implantable cardioverter defibrilla Ir. Different
haemodynamic and physiopathologic changes occur with tl ~use of these
mechanical circulatory assist devices and understanding of hese changes
is very important to help the surgeon, anesthetist, and p rfusionists to
decrease the morbidity of these changes on the patient.
A) Artificial cardiac pacemaker:
Electronic cardiac pacemakers are temporary Ir permanent
(implanted) devices that electrically stimulate the heart.
SlI1tIIIUlry
Pacemakers consist of a power source (battery) 1 tat supplies
energy for stimulation and other pacemaker functions, circuii ,for sensing
and regulation of stimulation, and leads that connect the I rwer source
and electronic circuitry to electrodes.
Artificial pacing is indicated for treatment of pen stent bradycardia
of any origin if it compromises hemodyramics or p edisposes to
ventricular irritability manifested by premature beats ( ventricular
tachycardia (VT). The two major indications for permane t pacing are
failure of impulse formation and failure of cardiac conductii 1. Clinically,
sick sinus syndrome and complete heart block are the r ost common
indications for pacemakers.
Complications following pacemaker or pcn imph ntation:
Earlv Late EaJ or late
Pneumo (hemo )-thorax Thromboembolism, pulse Lead disk
subcutaneous emphysema generator erosion, lead pacemake
myocardial perforation defects t pacing thresholds pacemake
arterial lead placement battery depletion pacemake
brachial plexus injury generator
extracard
1gement
arrhythmias
infection
syndrome
nalfunction
.c stimulation
B) The intraaortic ballon pump:
The IABP is a catheter mounted intravascular devic s designed to
improve the balance between myocardial oxygen suppf and demand
while increasing systemic perfusion to a modest I egree, Other
components of IABP include a pump, a gas source, and a r icroprocessor
console.
The primary indications for IABP in cardiac surgi al patient are
inability to separate from CPB, poor haemodynamic Unction, and
ongoing ischaemia following CPB despite increasing lrug support.
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SlI1IUIUIry
Myocardial function often improves with the use of thl IABP, and
systemic perfusion and vital organ function are preserved. I is crucial to
control heart rate and suppress atrial and ventricular dys hythmias to
ensure proper balloon timing. As cardiac function returns, tl ~assist ratio
is gradually weaned from every beat to every other bel and so on
assuming no further cardiac deterioration, then removed.
Complications associated with the lAP are pnmar y related to
ischaemia distal to the site of balloon insertion. Direct 1 auma to the
vessel, arterial obstruction, and thrombosis are the II ,st common
complications, although aortic perforation and balloon I ipture occur
rarely. Platelet destruction and thrombocytopenia may also I ccur,
C) Automatic implantable
Cardioverter defibrillator
Recurrent ventricular tachycardia or ventricular fibril uion that can
result in sudden death in the survivor of cardiac arrest may I : treated with
an automatic implantable cardioverter defibrillator (AICD)· iat senses the
onset of these ventricular dysrhythmias and delivers a syr hronized 25-
joule electrical discharge.
Table (11) Potential complications of len surger: :
I) Complications resulting II) Surgical complications III) Surgi
from the subclavian stick related to the pulse generator related 1
teehnique
Pneumothorax Pocket erosion Lead dislodi
Hemothorax Pocket hematoma Lead perofn
Subclavian artery puncture Pocket seroma Loose set sc
Air embolism Pocket infection Failure to is
Bleeding Microdisloc
Hemoptysis Malposition
Brachial plexus injury Diaphragms
Subclavian artriovenous fistula Exit block
Conductor!
Insulation b
Venous thrc
Pulmonary
.1 complications
the ICD leads
ment
Ion
,w
ate the set screw
ion
c stimulation
IClure
ale
ibosis
nbolism
SumtlUlry
Contraindications:
Implantation of an ICD is contraindicated in any pati at who has a
remedial cause of ventricul arrhythmias such as acut myocardial
infarction, myocardial ische ia, electrolyte imbalance, I ug toxicity,
hypoxia, or sepsis.
D) The ventricular assis
The VAD is a blood p p that is designed to assist r replace the
function of either the right or left ventricle. In the absence I f right or left
ventricular ejection, the RV supports the pulmonary eire ilation, while
a LVAD provides systemic p rfusion respectively. Implant: lIeVADs are
positioned intracorporeally i the anterior abdominal wa or within a
body cavity other than the pe icardium.
Extraeorporeal VADs ay be located in a paracorp real position,
along the patient’s anterior a dominal wall, or externally, 1 the patient’s
bedside.
Infrequently,
demands despite maximal p
is unable to meet syster IC metabolic
armacologic therapy and in ertion of the
ces, devices that actually pu np blood and
bypass either the left or ri t ventricle are required. The e devices are
effective because the inj producing myocardial dysi motion takes
place intraoperatively and, ore important, is often revers ile, A second
group of patients who have hown benefit from assist de’ ces are those
with chronic heart failure. These devices allow for I iemodynamic
support as a temporary meas re prior to heart transplantatic 1.
Complications of V s are inadequate LVAI flow, right
ventricular failure, haemorrh ge, thromboembolism, infectic t, multisystem
organ failure, device malfunc ion, and pump dependency.