MICRA - Increasing the pace of pacemaker technology/ MICRA - stimulatorul cardiac de marimea unei pastile/

Una dintre realizarile anului 2016 in tehnologie medicala este MICRA: cel mai mic stimulator cardiac (pacemaker) din lume. 

Cu 93% mai mic decat marimea unui pacemaker standard, MICRA are dimensiunea unei pastile. Revolutionara nu este doar dimensiunea extrem de mica, ci si implantarea acestuia direct in interiorul inimii. 
 

Stimulatoarele cardiace conventionale au rolul de a controla ritmul cardiac prin intermediul unor impulsuri electrice: cand bataile inimii sunt prea rapide, prea incete sau neregulate, impulsurile electrice generate de stimulator au rolul de a restabili ritmul cardiac la frecventa normala. 

Stimulatorul conventional este plasat sub piele, in zona inimii. Impulsurile generate sunt transmise catre inima prin intermediul unor fire, care au la capete electrozi (capetele care ajung la inima). Firele ajung la inima printr-o vena, electrozii fiind plasati pe peretele inimii: atriul drept, ventriculul drept sau pe ambele ventricule, in functie de tipul de aritmie al pacientului. Desi complicatiile sunt destul de rare, exista totusi riscul ca electrozii sa se rupa, deplasa, sau infecta, aceasta necesitand interventii ulterioare. 

 

Spre deosebire de stimulatoarele cardiace clasice, dimensiunea extrem de mica a stimulatorului MICRA face posibila implantarea acestuia direct in peretele inimii. Astfel se renunta la firele si electrozii unui stimulator clasic. 

 

Mai mult decat atat, implantarea se face minim-invaziv, cu ajutorul unui cateter introdus prin vena femurala a piciorului. Cateterul directioneaza stimulatorul direct in ventriculul drept al inimii, atasandu-l in peretele acestuia. Se reduc astfel riscurile asociate cu plasarea acestuia sub piele. 

 

MICRA functioneaza  ca orice pacemaker clasic, ajustand bataile inimii prin generarea de impulsuri electrice, avand o autonomie de pana la 12 ani. 

 

Persoanele cu stimulatoarele cardiace conventionale nu pot fi investigate cu tehnici de rezonanta magnetica nucleara (RMN) pe cand persoanele cu MICRA pot.  

 

Exista totusi si cateva dezavantaje. 

Majoritatea stimulatoarelor clasice sunt “bicamerale”: contin 2 fire cu 2 electrozi, unul plasat pe atriul drept si celalalt pe ventriculul drept stimuland in felul acesta atat camerele superioare cat si cele inferioare ale inimii. 

Spre deosebire de acestea, MICRA este “unicameral”: fiind plasat in peretele ventriculului drept. 

 

Dezavantajul major il reprezinta costul acestuia:  in jur de 10.000 de dolari, facandu-l inaccesibil pentru multi pacienti. 

 

MICRA este rezultatul unei cercetari de 10 ani a companiei Medtronic si reprezinta un progres major in aceasta tehnologie care ramasese neschimbata de zeci de ani. 

 

Contraindicatii

MICRA nu este indicat urmatoarelor categorii de persoane: celor care au deja implantat un filtru de vena cava inferioara sau o valva mecanica tricuspida, care au deja implantat un alt pacemaker sau un defibrilator (acestea interferand cu MICRA). Este contraindicat si persoanelor care prezinta intoleranta la heparina sau materialelor din care este construit device-ul. 



MICRA - Increasing the pace of pacemaker technology

 

One of the breakthroughs of 2016 in medical technology is MICRA: the world’s smallest cardiac pacemaker. 

With 93% smaller than a conventional pacemaker, MICRA has the size of a vitamin capsule.

Besides its small size, revolutionary about MICRA is its position inside the heart’s ventricle.  

 

Conventional artificial pacemakers control the cardiac rate through electrical impulses: when the heart rate is too low, too high or irregular, the pacemaker’s self-generated electrical impulses adjust the heart rate to a normal frequency. 

 

The conventional pacemaker is placed under the skin of the chest (near the heart) through a small incision.

The electrical impulses are transmitted to the heart through some wires (leads) with electrodes on one of the ends of these leads (the end which goes towards the heart). The leads reach the heart through a large vein after which the electrodes are placed on the heart’ s walls: either the right atrium, the right ventricle, or on both, according to the type of the arrythmia (irregularity in the heart rate). 

Though not often, complications may appear such as breakage, displacement or infections of the electrodes, after which further interventions could be necessary.  

In contrast to conventional pacemakers, the extremely small dimensions of MICRA make possible its implantation into the ventricle as a whole. Therefore with MICRA, no leads and electrodes are used anymore.

Moreover, the implantation procedure is minimally invasive, through a catheter introduced into the femural vein (in the upper leg, instead of the chest area). The catheter directs the pacemaker to the right ventricle, attaching it to its wall. In this way, MICRA reduces the risks related to placement under the skin. 

MICRA works as any other conventional pacemaker, monitoring the heart beats through electrical impulses, having a (machine-)life expectancy of 12 year . 

MICRA-wearers are also able to undergo MRI scans. This is contrary to the conventional pacemakers, which cannot be used while undergoing MRI scans.


However, there are also a few disadvantages. 

 Most of the standard pacemakers are “dual-chamber”: there are 2 leads with 2 electrodes. One for the right atrium and one for the right ventricle, stimulating both heart chambers: the “inferior” and “superior” ones. 

MICRA is only active in one chamber, being placed solely in the right ventricle. 

 

The biggest disadvantage of MICRA remains its cost: around $10.000., making it inaccessible for most people. 

 

MICRA is the result of 10 years of research by Medtronic and represents a major breakthrough in this technology, which had remained unchanged for decades.

 

Contra-indications: 

 

MICRA is not indicated for the following categories of people: those who already have implanted an inferior vena cava filter or a mechanical tricuspid valve, which have already implanted another (conventional) pacemaker or defibrillator (risk of interference with MICRA). It is contra-indicated to those who show intolerance to heparin, or materials used to build the device.