A pacemaker (HSM; Schrittmacher, SM) or pacemaker (PM) is a generator used in various cardiac diseases to correct the underlying cardiac arrhythmias. The functions of a pacemaker are stimulation (delivery of an electrical impulse, on demand) and sensing (perception) of intrinsic actions. At initial implantation, the average pacemaker patient is about 78 years old; about 17% of patients are younger than 70 years.
Indications (areas of application)
- Atrioventricular block (AV block) – conduction disturbances from the atrium to the ventricle.
- Bradyarrhythmia – slowed and irregular heart rate.
- Bradycardic arrhythmia following myocardial infarction (heart attack).
- Bradycardic atrial fibrillation (bradyarrhythmia absoluta).
- Brady tachycardia syndrome
- Intraventricular block (synonyms: IV block; fascicular block; thigh block) – conduction disturbance of the heart below the His bundle (lat. fasciculus atrioventricularis) including alternating thigh block (alternation between right and left bundle branch block) regardless of the presence of symptoms (Class I indication, Level of Evidence: C).
- Heart failure (cardiac insufficiency):
- Symptomatic heart failure (NYHA II-III), an LVEF (left ventricular ejection fraction/pump function) ≤ 35% (despite optimal drug therapy), ischemic etiology (cause of reduced blood flow), and more than 40 days after acute myocardial infarction (heart attack).
- Symptomatic heart failure (NYHA II-III), an LVEF ≤ 35% (despite optimal drug therapy), and non-ischemic cardiomyopathy (heart muscle disease).
- Patients (AHA stage B and / or NYHA I) with ischemic cardiomyopathy, an LVEF ≤ 30% (despite optimal drug therapy), and more than 40 days after acute myocardial infarction.
- Patients (AHA stage C and/or NYHA I) with an LVEF ≤ 30% (despite optimal drug therapy) and more than 40 days after acute myocardial infarction
- Sick sinus syndrome – syndrome of the sick sinus node.
- Sinuatrial block (SA block) – conduction disturbances between the sinus node and the atrium.
- Syncope (momentary loss of consciousness).
- With an ejection fraction > 35 percent (IIa recommendation).
- With hypertrophic cardiomyopathy (myocardial disease) and high risk of acute cardiac death (Grade I recommendation).
- Arrhythmogenic right ventricular cardiomyopathy (recommendation IIb).
- Atrioventricular reentry tachycardia with/without preexcitation – short-term tachycardia (accelerated pulse) due to conduction of excitation via short-circuit pathways.
- Asystole (acute cardiac arrest)
In bold, the most common pacing indications
The procedures
Pacemaker therapy is either temporary (time-limited) or permanent.In the temporary pacemaker, the device is left outside the patient; in the permanent pacemaker, the device, which is a few centimeters in size, is implanted under the skin slightly below the left or right clavicle.The electrodes in both types are passed transvenously (through the veins) to the right atrium or right ventricle (heart chamber), where they register the heart rhythm. In the case of the biventricular pacemaker, a third electrode is advanced via the right atrium and the coronary vein sinus (which returns the venous blood of the heart to the circulation and usually opens at the bottom of the right atrium) to the posterolateral wall (posterior side wall) of the left ventricle.The pacemaker can thus react specifically when the heart beats at a rhythm other than the preset one. There are several types of pacemakers:
- Frequency-stable pacemaker (fixed-frequency pacemaker) – this pacemaker emits a preset number of pulses per minute; practically no longer used today.
- Demand pacemaker (demand pacemaker) – the demand pacemaker only jumps in when the endogenous rhythm is interrupted
In addition to this classification, the demand-controlled pacemaker is classified according to the stimulation site, detection site (sensing/signal recording), and operating mode (mode of action):
- P- or atrial-gated pacemaker: two variants:
- P-wave inhibited atrial demand pacemaker (AAI pacemaker: stimulation site = atrium/atrial, sensing/perception site = atrium, mode of operation = inhibition/inhibition; used only with intact AV conduction); indications: Bradycardia, SA block, sick sinus syndrome, and atrial flutter.
- P-wave-triggered ventricular pacemaker (VAT pacemaker: stimulation site = ventricle/major chamber, sensing site = atrium, mode of operation = T-triggering/triggering a function), in which the potential sensed by the cardiac ear is transmitted to the ventricle/cardiac chamber via a second probe after an appropriate delay.
- Ventricular-controlled pacemaker: from the R-wave or QRS complex:
- Pacemaker with pulse triggered by the R-wave (VVT pacemaker: stimulation site: ventricle, sensing site = ventricle, mode of operation = T-triggering; formerly called “stand-by pacemaker”).
- QRS- or R-inhibited demand pacemaker (VVI pacemaker: pacing site: ventricle, sensing site = ventricle, operating mode = inhibition); most common model; pulse delivery occurs only in the absence of the next potential within a set time
Sequential pacemaker (bifocal pacemaker): in which successive pulse delivery to the atrium and ventricle occurs at physiological intervals (dual-chamber or double-chamber pacing); two variants:
- AV-sequential, R-wave inhibited pacemaker (DVI pacemaker: stimulation site = dual, ie, atrium and ventricle, sensing site = ventricle, mode of operation = inhibition).
- Optimized AV sequential pacemaker (DDD pacemaker: pacing site = dual, ie, atrium and ventricle, sensing site = dual, ie, atrium and ventricle, mode of operation = dual, ie, inhibition and T triggering).
All pacemaker types trigger a pulse only when the endogenous rhythm drops below the pacemaker base rate. In primary prophylaxis, the defibrillator allows relative risk reductions of 20-30%, and in secondary prophylaxis, relative risk reductions of 20-40% are known. Cardiac resynchronization therapy (CRT) leads to an improvement of heart failure symptoms (cardiac insufficiency symptoms) and prognosis. After insertion of a pacemaker, check-ups are performed at regular intervals (every six to twelve months) to detect possible complications at an early stage.The pulse generator is changed after 5-8-10 years, leaving the probe in place.
Electromagnetic interference sources
Interference with implants occurs in approximately 0.3-0.7 cases per year. The following are notes on electrical devices
- Cellular phones (only possible now if the cell phone is placed directly on the skin site above the implant).
- Anti-theft devices (in the entrance area of department stores): a safety distance is required for radio-frequency systems (so-called RFID scanners):
- Pacemaker 60 cm
- Defibrillator 40 cm
- Induction stoves: safety distance of at least 25 cm.
Possible complications
Early complications after pacemaker implantation:
- Ventricular perforation (“piercing of the ventricle”) with pericardial tamponade (accumulation of fluid in the pericardium leading to obstruction of filling of the heart) (<1%)
- Pneumothorax (collapse of the lung caused by an accumulation of air between the visceral pleura (lung pleura) and the parietal pleura (chest pleura)) (0.4%)
- Dislocation (“displacement”) of electrodes (<1%).
To possible infections (1-12%) after implantation of a pacemaker may occur in wound healing disorders or in the wake of pressure necrosis.Late complications after pacemaker implantation:
- Generator malfunctions (insufficient signal perception by the pacemaker: “undersensing” (3.8%); responding to signals not intended for this purpose (e.g. T-wave): “oversensing”, (0.7%)).
- Electrode system malfunctions (electrode dislocation; electrode rupture (3.8%); housing rupture; insulation defects (3.4%))
- Battery exhaustion
Symptoms of pacemaker dysfunction
- Dizziness or syncope (momentary loss of consciousness) when pacing fails
- Exertional dyspnea in the event of battery exhaustion
- Tachycardia in pacemaker tachycardia.
- hemodynamic instability
Leading symptoms and possible pacemaker-associated differential diagnoses (modified from)
| Leading symptoms | Pacemaker-associated differential diagnoses | Measures |
| Bradycardia(heartbeat too slow: < 60 beats per minute)Syncope (momentary loss of consciousness) | SM dysfunction: “exit block” (= ineffective stimulation; spikes are not followed by a response),battery depletion,SM inhibition due to “oversensing (= SM picks up electrical (interference) signals from outside, which are stronger than the heart’s own impulses; e.g., razor) | ECG, magnetic rest if necessary (= increases pacing frequency and pulse energy; caveat: high energy consumption can lead to total SM failure), external SM, catecholamine administration |
| Dyspnea(shortness of breath) | SM dysfunction, pneumothorax (collapse of the lung caused by an accumulation of air between the visceral pleura (lung pleura) and the parietal pleura (chest pleura)), pericardial effusion (pericardial effusion) | ECG, pulse oximetry (method of noninvasively determining arterial oxygen saturation by measuring light absorption), chest x-ray, echocardiography (cardiac ultrasound) |
| Tachycardia(> 100 heartbeats per minute). | SM tachycardia | ECG, magnetic rest |
| Chest pain(chest pain) | Acute coronary syndrome (AKS; ACS) | ECG, transport to center with cardiac catheterization laboratory. |
| Fever, chills | Pocket infection, probe endocarditis | SM pocket inspection,echocardiography, blood culture. |
SM = pacemaker
Long-term consequences
- Heart failure (cardiac insufficiency)
Other notes
- Wireless pacemakers (“leadless pacers”), which are miniaturized pacemakers implanted completely in the apex of the right ventricle (heart chamber), have a 66% lower complication rate than after implantation of transvenous pacing systems at 6 months in a large comparative study of more than 5,700 patients. The pneumothorax rate (see above), which was surprisingly high in the conventional pacemaker group (5.4% versus 0%), was responsible for the significant difference….
- Pacemakers that stimulate the His bundle (= His bundle pacemakers) significantly reduce the risk of heart failure-related hospitalization. Furthermore, a trend towards lower mortality (death rate) is evident in the long-term course.