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Myocardial Infarction and its Treatments

Presenter : S.Mohammad ZargarSupervisor : Dr. Mahdikhani

Faculty of EngineeringDepartment of Biomedical Engineering

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Treatments

Surgeries and procedures for atherosclerosis include:

Angioplasty Stent placement Coronary Artery Bypass Grafting surgery (CABG) Atherectomy

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CABG

Coronary artery bypass grafting (CABG) is a type of surgery - where arteries or veins from other areas in the body are used to bypass the narrowed coronary arteries. CABG can improve blood flow to your heart, relieve chest pain, and possibly prevent a heart attack.

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Atherectomy

Unlike angioplasty and stents, which push plaque into the vessel wall, atherectomy cuts plaque from the wall of the artery. While atherectomy is usually employed to treat arteries it can be used in veins and vascular bypass grafts as well.

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Angioplasty

In the late 1970s, doctors began using balloon angioplasty to treat coronary arteries that got too narrow.

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Coronary StentsBecause no new support is left, in a small percentage of cases, the artery will regain its previous shape or even collapse after the balloon is deflated. About 30% of coronary arteries treated with balloon angioplasty get narrower again.To solve these problems, small stents were created that could be mounted on the balloon and put into a blood vessel. The stent expands when the balloon is inflated, locks into place, and forms a permanent scaffold to hold the artery open after the balloon is deflated and removed.

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BMS

First-generation stents were made of bare metal. Although they almost eliminated the risk of the artery collapsing, they only modestly reduced the risk of re-narrowing.

About a quarter of all coronary arteries treated with bare-metal stents would close up again, usually in about 6 months.

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DESStents coated with drugs that interrupted the re-narrowing are called drug-eluting stents.

While bare-metal stents (BMS) are still utilized, drug-eluting stents (DES) now offer clinicians the ability to prevent restenosis via a different mechanism.

Advantages: In clinical trials, these

reduced re-narrowing cases to less than 10%. They also lowered the need for repeat procedures for people with diabetes, who have a bigger chance of their arteries getting narrow again.

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First Generation DES

First-generation DES include sirolimus-eluting stents

(SES; 2003) and paclitaxel-eluting stents (PES; 2004).

SES and PES revolutionized rates of restenosis after

cardiac procedures. These stents were developed to

prevent the proliferation of smooth-muscle cells and other

cell types seen with restenosis.

PES and SES were compared in several clinical trials, most

of which concluded that SES were associated with lower

rates of clinical restenosis and late lumen loss. The

superiority of SES may be due to differences in mechanism

of action, timing of drug delivery, and cellular inflammatory

response for SES and PES at sites of overlapping stents.

Sirolimus

Paclitaxel

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Second Generation DES Second-generation DES, including

zotarolimus- and everolimus-eluting

stents (ZES, EES), were approved for

use in the United States in 2008.

The newer stents, EES and ZES, are

thinner and more flexible and have a

cobalt-chromium alloy platform, which

makes them more deliverable than the

first-generation stents. These stents may

also be more biocompatible, thereby

generating less inflammatory response

and faster vessel endothelialization.

Zotarolimus

Everolimus

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DES

Although the underlying principle of DES remains constant, each type may offer variations with respect to deliverability (ease of placement), efficacy (preventing restenosis), and safety (thrombosis rates). The use of dual antiplatelet therapy (DAPT) with stents has significantly improved outcomes in patients undergoing PCI.

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Still, there were concerns that drug-eluting stents were associated with a rare but serious complication called in-stent thrombosis. This is where a blood clot forms in a stent one or more years after it's implanted.

Because this complication can be fatal, it’s important that people with drug-eluting stents take aspirin and an anticlotting drug as prescribed until a doctor tells them to stop.

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Dual Antiplatelet TherapyCoronary rethrombosis and coronary restenosis are sequelae of stent placement. Coronary rethrombosis is defined as reocclusion of coronary vessels by thrombin formation, and coronary restenosis is reocclusion of coronary vessels and smooth-muscle endothelial overgrowth. These sequelae can lead to devastating events such as MI and death. DES are associated with a reduced risk of restenosis but an increased risk of rethrombosis, specifically with early discontinuation of DAPT.Dual antiplatelet therapy (DAPT) = Combination of aspirin and a P2Y12. platelet receptor inhibitor to prevent stent thrombosis after a. percutaneous coronary intervention. 2. Percutaneous coronary intervention (PCI) = reperfusion of a coronary.

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Third-Generation Stents

if the BVS absorbed into the vessel wall over the next year, we would expect a number of great things that the vessel might resume some or most of its normal function.

A bioresorbable, biodegradable, or bioabsorbable stent is manufactured from a material that may dissolve or be absorbed in the body.

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Hot Tip

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Damaged Cardiac TissueCardiac tissue damage due to myocardial infarction (MI) is one of the leading causes of mortality worldwide. the body’s natural response after MI is a process of fibrous remodeling that ultimately leads to scar formation instead of functional myocardium formation. This scar formation prevents the heart from functioning properly and eventually leads to complete heart failure.

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Myocardial Infarction

Pharmaceutical therapy

Medical devices

Transplantation

Limitations• High Invasiveness

• scarcity of donor organs

• prolonged hospitalization time

Limitations

• thrombosis or stenosis of devices

• immune rejection

Treatments of MI

Tissue engineered organ

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CV TERM

As a result, there is a huge need for developing new solutions to repair or replace damaged cardiac tissues. Injectable hydrogels have emerged as a promising approach for cardiac repair in regenerative medicine.

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CV RMIn regenerative medicine approach, the appropriate cell types are injected to the injured myocardium. These cells can be progenitor cells or stem cells that can be differentiated into the necessary cardiac cell types or even fully differentiated cardiac cells. Some biomaterials-alone can be injected near the infarcted heart tissue to provide the mechanical support to the injured heart tissue.

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CV TE

In tissue engineering, the

desired cell types are

grown in some natural or

synthetic biomaterials or

sometimes even without

any biomaterials, for the in

vitro formation of cardiac

tissue that could be

implanted around the

damaged areas of heart.

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Hydrogels

Hydrogels are “water-swollen polymer networks” that have a high percentage of water content identical to human tissues.

They can be injected as a liquid and be crosslinked to a gel phase using certain physical or chemical stimuli.

In situ cross-linking Methods: Thermo-sensitive hydrogels photo cross-linking pH-dependent Crosslinking Ionic crosslinking

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Design Parameters in synthesis of Hydrogels

Biocompatible

Biodegradable

Bioresorbable

Not triggering an immune response

Contractible

Elastic

Able to sustain periodic contraction and relaxation

Well-vascularizes

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