More than 3 million people in the United States alone rely on a pacemaker to regulate their heart rhythm. While the battery may be the most recognizable component in the system, capacitors are just as essential to ensure these implantable devices function safely and reliably over time.
Found in every critical functional block, shown in Figure 1, capacitors do what they do best to keep the heart on beat: manage energy, suppress noise, and help regulate timing.
Figure 1: Primary electrical blocks in an implantable pacemaker, showing signal flow from sensing through pulse delivery via the amplifier, timing, and output driver circuits.
A pacemaker’s leads pick up the heart’s natural electrical signals. Since the input signals are small and noisy to start, the sensing amplifier is responsible for amplifying and filtering them such that the pacemaker can detect relevant heart signals (e.g., R-waves of an ECG) without interference.
Capacitors form a portion of the bandpass filters that amplify those relevant heart signals and block electromagnetic interference (EMI) and other DC components. They also store energy during voltage spikes and release it during drops to maintain signal integrity.
As the name implies, the timing circuit acts as a clock for the pacemaker, determining when to send electrical pulses to maintain healthy heart rhythms. If no heartbeat is detected within the expected timespan, the timing circuit triggers the pacemaker to send a pulse.
Made up of resistors and capacitors, RC timing circuits control the interval of time between pulses, and the capacitor’s charge/discharge cycle sets the pacemaker’s base beat per minute. In modern pacemakers, oscillators or microcontrollers augment or replace discrete RC circuits for timing stability.
When triggered by the timing circuit, the output driver generates a small electrical pulse that travels through the leads to the heart muscle, causing it to contract and produce a heartbeat. The output driver covers pulse shaping and DC blocking to ensure the pulse is strong enough to stimulate the heart without damaging the tissue.
A coupling capacitor protects cardiac tissue from unwanted simulation by blocking harmful DC current from reaching the heart while allowing AC pulses to pass. Coupling capacitors also help reduce polarization voltages at the electrode-tissue interface in between pulses, helping restore baseline conditions for accurate sensing. Reducing residual charge is critical for preventing sensing errors caused by unwanted noise.
The pacemaker is powered by a small battery that provides steady voltage to all circuits and specialty components. Lithium-based batteries provide long-term, low-drain power, while capacitors supply short bursts of high current during stimulation, compensating for the battery’s limited peak current. In some designs, capacitors charge in parallel and discharged in series to boost voltage.
Multi-layer ceramic capacitors (MLCCs) offer support in each of these size-constrained functional blocks. They fit into the sensing amplifier for filtering and noise suppression. With a high capacitance-to-size ratio, they can set precise timing intervals in the timing circuit with less board space. When placed near integrated circuits or microcontrollers, they smooth voltage fluctuations and filter noise to protect sensitive components. In the effort to miniaturize pacemaker design (e.g., leadless pacemakers), the size and effectiveness of each component can’t be overlooked.
Ready to explore capacitor options engineered specifically for implantable devices? Start by reviewing the MD Series Medical-Grade Capacitors portfolio to see how these components support key pacemaker functions. Request sample devices to evaluate performance in your own testing environment.