This document summarizes various implanted medical devices. It discusses pacemakers, implantable cardioverter defibrillators, coronary stents, and techniques for treating brain aneurysms. Pacemakers are used to treat heart rhythm issues and maintain suitable heart rate. ICDs monitor heart rhythm and deliver shocks to restore normal rhythm if needed. Coronary stents prop open arteries and may be bare metal or coated to prevent reblockage. Aneurysms can be treated with surgical clipping or endovascular coiling to isolate the aneurysm from blood flow.

1. Implanted Devices
Dr Pavan Acharya
Resident Doctor,
SVPIMSR
Ahmedabad

2. Pacemakers:
• A pacemaker is a small device that sends electrical impulses to the
heart muscle to maintain a suitable heart rate and rhythm.
• A pacemaker may also be used to treat fainting spells (syncope),
congestive heart failure, and hypertrophic cardiomyopathy.
• Pacemakers are implanted just under the skin of the chest during a
minor surgical procedure.

3. • The pacemaker has two parts: the leads and a pulse generator.
• The pulse generator houses the battery and a tiny computer, and
resides just under the skin of the chest.
• The leads are wires that are threaded through the veins into the
heart and implanted into the heart muscle. They send impulses from
the pulse generator to the heart muscle, as well as sense the heart's
electrical activity.
• There are different types of pacemakers:
• Single-chamber pacemakers use one lead in the upper chamber
(atria) or lower chamber (ventricles) of the right side of the heart.
• Dual-chamber pacemakers use one lead in the right atrium and one
lead in the right ventricle of your heart.
• Biventricular pacemakers use three leads: one placed in the right
atrium, one placed in the right ventricle, and one placed in the left
ventricle (via the coronary sinus vein).

5. NBG Code:
• The pacemaker nomenclature established by the North American
Society of Pacing and Electrophysiology (NASPE) and the British
Pacing and Electrophysiology Group (BPEG) is designated as NBG code
for pacing nomenclature

7. Examples:
• Pacing mode VVI (VVIOO):
(V) Ventricular Pacing, (V) Ventricular Sensing, (I) Pacing inhibited by
sensed spontaneous Ventricular depolarizations, (O) No rate
modulation, (O) No multisite pacing.
• This mode is often used in patients with Permanent Atrial Fibrillation
and complete AV Block or severe bradycardia.
• Pacing mode DDDR (DDDRO):
(D) Atrial and Ventricular Pacing, (D) Atrial and Ventricular Sensing, (D)
Inhibited by atrial or ventricular sensing and ventricular pacing triggered
after an atrial sensing, (R) Rate modulation, (D) No multisite pacing.
• This mode is often used in patients with Sick Sinus Syndrome or
Atrioventricular Blocks

8. • AOO, VOO or DOO: Asynchronous Atrial, Ventricular or Dual pacing; no
sensing, rate modulation, or multisite pacing.
• AAI: Atrial pacing inhibited by sensed spontaneous atrial depolarizations;
no rate modulation or multisite pacing.
• DDD: Dual chamber pacing (normally inhibited by atrial or ventricular
sensing during the alert portion of the VA interval or by ventricular sensing
during the alert portion of the AV interval, and with ventricular pacing
triggered after a programmed PV interval by atrial sensing during the alert
portion of the VA interval); no rate modulation or multisite pacing.
• DDDR: Dual chamber, adaptive-rate pacing; no multisite pacing.
• DDDOV: Dual chamber pacing without rate modulation, but with multisite
pacing (i.e., biventricular pacing, more than one pacing site in one
ventricle, or both features).
• VVIRV: Ventricular inhibitory pacing with rate modulation and multisite
ventricular pacing (i.e., biventricular pacing or more than one pacing site in
one ventricle). This mode is often used in patients with heart failure,
Chronic Atrial Fibrillation, and Intraventricular Conduction Delay

9. • Pacemakers are implanted two ways:
• Endocardial approach. This is the most common technique used.
• A local anesthetic (pain-relieving medication) is given to numb the area. An incision is
made in the chest where the leads and pacemaker are inserted.
• The lead(s) is inserted through the incision and into a vein, then guided to the heart
with the aid of the x-ray machine.
• The lead tip attaches to the heart muscle, while the other end of the lead (attached to
the pulse generator) is placed in a pocket created under the skin in the upper chest.
• Epicardial approach. This technique is more commonly used in children than
adults.
• A surgeon performs this procedure in an operating room. General anesthesia is given.
• The surgeon attaches the lead tip to the heart muscle, while the other end of the lead
(attached to the pulse generator) is placed in a pocket created under the skin in the
abdomen.
• Although recovery with the epicardial approach is longer than that of the transvenous
approach, minimally invasive techniques have enabled shorter hospital stays and
quicker recovery times.

10. Indications of temporary pacemakers:
• Reversible causes of heart block that may call for temporary cardiac pacing
include the following:
• Injury to the SA node or other parts of the conduction system after cardiac
surgery (injuries that occur after coronary bypass surgery tend to be
temporary, but those sustained after valve surgery or cardiac transplant
may not be reversible)
• Chest and cardiac trauma associated with either temporary SA node or AV
node dysfunction
• Metabolic and electrolyte derangements (eg, hyperkalemia)
• Drug-induced bradyarrhythmia (eg, digitalis toxicity); if treatment with the
drug must be continued and there is no alternative, permanent pacing
should be considered
• Other diseases (eg, Lyme disease, bacterial endocarditis) that may be
associated with temporary damage to the SA node or the AV node

11. Contraindications:
• In general, temporary cardiac pacing should not be considered for
asymptomatic patients who have a fairly stable rhythm (eg, a first-
degree AV block or a Mobitz I or stable escape rhythm). For example,
pacing an asymptomatic patient with a stable escape rhythm may
render that individual dependent on pacing, and withholding pacing
may then cause asystole.
• Although the aforementioned rhythms are stable for the most part,
there are exceptions (eg, a Mobitz I rhythm with a wide QRS may
originate from an infra-AV nodal area and therefore may progress to
complete heart block).

12. Indications of Permanent Pacemakers
• Acquired Atrioventricular Block in Adults
• Chronic Bifascicular and Trifascicular Block
• Atrioventricular Block Associated With Acute Myocardial Infarction
• Sinus Node Dysfunction
• Termination of Tachyarrhythmias by Pacing
• Hypersensitive Carotid Sinus and Neurally Mediated Syndromes

13. Implantable Cardioverter Defibrillators (ICD):
• ICD is an electronic device that constantly monitors your heart rate
and rhythm. When it detects a very fast, abnormal heart rhythm, it
delivers energy to the heart muscle. This causes the heart to beat in a
normal rhythm again.
• The ICD has two parts: the lead(s) and a pulse generator. The lead(s)
are made up of wires and sensors that monitor the heart rhythm and
deliver energy used for pacing and/or defibrillation (see below for
definitions). The generator houses the battery and a tiny computer.
Energy is stored in the battery until it is needed. The computer
receives information from the leads to determine how the heart is
beating.

15. • There are different types of ICDs, including:
• Single-chamber ICD. A lead is attached in the right ventricle. If
needed, energy is delivered to the ventricle to restore a normal heart
rhythm.
• Dual-chamber ICD. Leads are attached in the right atrium and the
right ventricle. Energy can be delivered to the right atrium and then to
the right ventricle, helping your heart to be paced in a normal
sequence.
• Biventricular ICD. Leads are attached in the right atrium, the right
ventricle and the coronary sinus, adjacent to the left ventricle. This
technique helps the heart beat in a more efficient way and is
specifically used for patients with heart failure

16. • How Does an ICD Work?
• The ICD monitors the heart rhythm, identifies abnormal heart
rhythms, and determines the appropriate therapy to return your
heartbeat to a normal rhythm:
• Antitachycardia Pacing (ATP). When the heart beats too fast, a series
of small electrical impulses are delivered to the heart muscle to
restore a normal heart rate and rhythm.
• Cardioversion. A low-energy shock is delivered to restore a normal
heart rhythm.
• Defibrillation. When the heart is beating dangerously fast, a high-
energy shock is delivered to the heart muscle to restore a normal
rhythm.
• Bradycardia pacing. When the heart beats too slow, small electrical
impulses stimulate the heart muscle to maintain a suitable heart rate.

17. Indications:
• ICDs are used for:
• People who have had an episode of sudden cardiac arrest or
ventricular fibrillation.
• People who have had a heart attack and are at high risk for sudden
cardiac arrest.
• People who have hypertrophic cardiomyopathy and are at high risk
for sudden cardiac arrest.
• People who have dilated cardiomyopathy with severely reduced heart
function and are at high risk for sudden cardiac arrest.
• People who have had at least one episode of ventricular tachycardia,
an abnormal heart rhythm.

18. Pacemakers vs ICDs
• The biggest difference between an ICD and pacemaker is that an ICD
continually monitors heart rhythm and can send low- or high-energy
electrical pulses to correct an abnormal heart rhythm. ICDs will
initially send low-energy pulses to restore heart rhythm, but switch
to high-energy pulses when the low-energy shocks are ineffective.
• Pacemakers, however, only give low-energy electrical pulses to
restore regular heartbeat.

19. Coronary Stents:
• Stents are small, expandable tubes that treat narrowed arteries in
body. In people with coronary heart disease caused by the buildup of
plaque, they can:
• Open narrowed arteries
• Reduce symptoms, like chest pain
• Help treat a heart attack

22. • There are currently five types of stents available:
• Dual Therapy Stent (DTS)
• Bioresorbable Vascular Scaffold (BVS)
• Bio-engineered Stent
• Drug Eluting Stent (DES)
• Bare Metal Stent (BMS)

23. • Bare Metal Stent
• Bare metal stents are usually stainless steel and have no special
coating. They act as scaffolding to prop open blood vessels after they
are widened with angioplasty. As the artery heals, tissue grows
around the stent, holding it in place. However, sometimes an
overgrowth of scar tissue in the arterial lining increases the risk of
re-blockage

24. • Drug Eluting Stent
• Drug Eluting Stents (DES) are coated with medication that is released
(eluted) to help prevent the growth of scar tissue in the artery lining.
This helps the artery remain smooth and open, ensuring good blood
flow and reduces the chances of the artery re-narrowing or
restenosis. However, it also leads to a higher chance of blood clots
(stent thrombosis).
• Due to a relatively slower healing process, patients implanted with
DES must strictly follow their doctor's recommendation on drug
therapy (DAPT) to help reduce risk of stent thrombosis. Current
American Heart Association recommendations are for a minimum
DAPT therapy of at least 12 months after DES implantation.

26. ACC/AHA Guideline Update(2016) on Duration
of Dual Antiplatelet Therapy:
• Recommendations in the document apply specifically to duration of
P2Y12 inhibitor therapy in patients with CAD treated with DAPT.
Aspirin therapy should almost always be continued indefinitely in
patients with CAD.
• Lower daily doses of aspirin, including in patients treated with DAPT,
are associated with lower bleeding complications and comparable
ischemic protection compared with higher doses of aspirin. The
recommended daily dose of aspirin in patients treated with DAPT is
81 mg (range 75–100 mg).

27. • In patients with stable ischemic heart disease (SIHD) treated with
DAPT after drug-eluting stent (DES) implantation, P2Y12 inhibitor
therapy with clopidogrel should be given for at least 6 months (Class
I). In patients with SIHD treated with DAPT after bare-metal stent
(BMS) implantation, P2Y12 inhibitor therapy (clopidogrel) should be
given for a minimum of 1 month (Class I).
• In patients with SIHD treated with DAPT after BMS or DES
implantation who have tolerated DAPT without a bleeding
complication and who are not at high bleeding risk (e.g., prior
bleeding on DAPT, coagulopathy, oral anticoagulant use), continuation
of DAPT with clopidogrel for longer than 1 month in patients treated
with BMS or longer than 6 months in patients treated with DES may
be reasonable (Class IIb).

28. • In patients with acute coronary syndrome (ACS) (non-ST elevation
[NSTE]-ACS or ST elevation myocardial infarction [STEMI]) treated with
DAPT after BMS or DES implantation, P2Y12 inhibitor therapy
(clopidogrel, prasugrel, or ticagrelor) should be given for at least 12
months (Class I).
• In patients with ACS (NSTE-ACS or STEMI) treated with coronary stent
implantation who have tolerated DAPT without a bleeding
complication and who are not at high bleeding risk (e.g., prior bleeding
on DAPT, coagulopathy, oral anticoagulant use), continuation of DAPT
(clopidogrel, prasugrel, or ticagrelor) for longer than 12 months may
be reasonable (Class IIb)

29. • Bio-engineered Stent
• Bio-engineered Stent is also known as antibody-coated stent. This
type of stent differs from DES because it does not contain a polymer
and does not use a drug. As a result, it helps to speed up the cell lining
of the artery (endothelialization), promoting natural healing.
• The antibody on the stent's surface attracts circulating Endothelial
Progenitor Cells (EPCs) which come from human bone marrow and
help speed up the formation of healthy endothelium. This provides
rapid coverage over the stent's surface helping to reduce the risk of
early and late thrombosis (blood clots).

30. • Bioresorbable Vascular Scaffold
• The Bio-Vascular Scaffold (BVS) is a drug eluting stent on a dissolvable
type of scaffold platform which can be absorbed by the body over
time.
• Like some of the currently available Drug Eluting Stents (DES), BVS is
coated with a drug released from a polymer that disappears over time
to reduce the likelihood of the artery re-narrowing (restenosis). The
scaffold itself is absorbed overtime. Unlike with the DTS, there is no
active element to promote artery healing.

31. • Dual Therapy Stent
• Dual Therapy Stent (DTS) is the latest type of coronary stent. It is a first-of-
its-kind stent therapy designed to not only reduce the likelihood of the re-
narrowing of the artery or of having to undergo a repeat procedure, but
also help the healing process of the artery. It combines the benefit of DES
and bio-engineered stents and is the only stent to contain a drug with
active healing technology.
• The DTS has coating both inside and outside, which reduces the likelihood
of blood clots, inflammation and helps the healing process of the artery.
• The stent surface facing the artery wall contains a drug that is released to
help stop the artery blocking again without the worry of swelling or an
inflammatory response. The drug is delivered from a bioresorbable
polymer that will degrade over time.
• The side of the stent which faces blood flow is coated with antibodies,
which promote natural healing and helps the healthy artery function
properly.

32. Aneurysmal Clipping:
• The goal of surgical clipping is to isolate an aneurysm from the normal
circulation without blocking off any small perforating arteries nearby.
Under general anesthesia, an opening is made in the skull, called a
craniotomy. The brain is gently retracted to locate the aneurysm. A
small clip is placed across the base, or neck, of the aneurysm to block
the normal blood flow from entering. The clip works like a tiny coil-
spring clothespin, in which the blades of the clip remain tightly closed
until pressure is applied to open the blades. Clips are made of
titanium and remain on the artery permanently.

34. Aneurysmal Coiling:
• The goal of endovascular coiling is to isolate an aneurysm from the
normal circulation without blocking off any small arteries nearby or
narrowing the main vessel. Endovascular describes the minimally
invasive technique of accessing the aneurysm from within the
bloodstream, specifically during angiography. The bloodstream is
entered through the large femoral artery in the upper leg (groin area).
A flexible catheter is advanced from the femoral artery to one of four
arteries in the neck that lead to the brain.

36. • Once the catheter reaches the aneurysm, a very thin platinum wire is
inserted. The wire coils up as it enters the aneurysm and is then
detached. Multiple coils are packed inside the dome to block normal
blood flow from entering. Over time, a clot forms inside the
aneurysm, effectively removing the risk of aneurysm rupture. Coils
remain inside the aneurysm permanently. Coils are made of platinum
and other materials, and come in a variety of shapes, sizes, and
coatings that promote clotting.

38. Julio Palmaz