10.1 Cardiovascular Implants (Pacemakers, Artificial Hearts)

Cardiac pacemakers and artificial hearts are life-saving devices for heart patients. Pacemakers regulate heart rhythm with electrical impulses, while artificial hearts replace or support failing hearts. These technologies have revolutionized treatment for bradycardia, heart block, and end-stage heart failure.

Implantation procedures range from minimally invasive for pacemakers to open-heart surgery for artificial hearts. While these devices significantly improve quality of life and prognosis, they come with risks like infection and device failure. Regular monitoring and follow-up care are crucial for optimal outcomes.

Pacemakers

Functions of cardiac pacemakers

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• Implantable devices regulate heart rhythm by delivering electrical impulses to the heart
  • Treat bradycardia (slow heart rate) and heart block (atrioventricular block)
• Main components include:
  • Pulse generator contains battery and electronic circuitry generates electrical impulses
  • Leads are insulated wires deliver electrical impulses from pulse generator to heart
  • Electrodes attached to ends of leads deliver electrical impulses to heart tissue
• Monitor heart's electrical activity through leads and electrodes
  • If heart rate falls below predetermined threshold, delivers electrical impulse to stimulate heart and maintain normal rhythm
• Operate in different modes depending on patient's needs
  • Single-chamber pacemakers stimulate either atrium or ventricle (AAI or VVI modes)
  • Dual-chamber pacemakers stimulate both atrium and ventricle, providing more physiologically natural heart rhythm (DDD mode)
  • Rate-responsive pacemakers adjust pacing rate based on patient's activity level, detected by sensors within device (AAIR, VVIR, DDDR modes)

Artificial Hearts

Types of artificial hearts

• Total Artificial Hearts (TAHs) replace entire heart used as bridge to transplantation or destination therapy for end-stage heart failure
  • Advantages: completely replace heart function and provide adequate blood flow
  • Limitations: require large external power source, increased risk of infection and thromboembolism, limited long-term durability
• Ventricular Assist Devices (VADs) support function of failing ventricle used as bridge to transplantation, recovery, or destination therapy
  • Left Ventricular Assist Devices (LVADs) support left ventricle, responsible for pumping oxygenated blood to body
  • Right Ventricular Assist Devices (RVADs) support right ventricle, pumps deoxygenated blood to lungs
  • Advantages: smaller and more portable than TAHs, can support single failing ventricle, improve patient quality of life
  • Limitations: risk of infection, thromboembolism, device malfunction; require careful anticoagulation management

Surgical Procedures and Complications

Implantation of cardiovascular devices

• Pacemaker implantation:
  1. Typically performed under local anesthesia with sedation
  2. Small incision made in chest wall, leads inserted through subclavian vein and guided to heart using fluoroscopy
  3. Pulse generator implanted in subcutaneous pocket, usually below collarbone
• Artificial heart implantation:
  1. Requires open-heart surgery under general anesthesia
  2. Native heart removed, artificial heart implanted and connected to atria, pulmonary artery, and aorta
  3. For VADs, device connected to appropriate ventricle and blood vessels without removing native heart
• Potential complications include:
  • Infection at implant site or systemic infection
  • Bleeding or hematoma formation
  • Pneumothorax (collapsed lung) during pacemaker implantation
  • Thromboembolism (blood clots) and stroke
  • Device malfunction or failure

Impact on Quality of Life and Prognosis

Impact of implants on patient outcomes

• Pacemakers significantly improve quality of life for patients with bradycardia or heart block by:
  • Relieving symptoms such as fatigue, dizziness, and syncope (fainting)
  • Preventing complications associated with untreated bradycardia, such as heart failure and sudden cardiac death
  • Enabling patients to resume normal activities and exercise
• Artificial hearts and VADs improve quality of life and prognosis for patients with end-stage heart failure by:
  • Restoring adequate blood flow and reducing symptoms such as dyspnea (shortness of breath), fatigue, and edema (swelling)
  • Allowing patients to be discharged from hospital and resume some daily activities
  • Serving as bridge to heart transplantation, increasing likelihood of survival until suitable donor heart becomes available
• Long-term prognosis depends on factors such as:
  • Underlying heart condition and comorbidities (other health issues)
  • Type of device implanted and its long-term performance
  • Patient adherence to anticoagulation therapy and device maintenance
  • Occurrence of complications such as infection, thromboembolism, or device failure
• Regular follow-up with cardiologist and device monitoring essential for optimal long-term outcomes and early detection of any complications or device issues