ECG Machine Testing – Is It the Machine or the Leads?

An Electrocardiogram (ECG) machine is an important diagnostic tool used in medical practices, hospitals and specialist healthcare facilities.

It records the electrical activity of the heart, providing information that healthcare professionals use when assessing cardiac function.

But what happens when an ECG machine isn't producing the results expected?

Is the machine faulty, or could the problem be something as simple as its patient leads?

At ClinicCheck, we've encountered situations where further investigation revealed that the ECG machine itself wasn't necessarily the problem.

When an ECG Machine Isn't Working Properly

At ClinicCheck, we've investigated at least two separate cases involving ECG machines that were not functioning correctly.

Both investigations were undertaken outside the routine annual equipment verification programme.

Using an ECG signal simulator, we were able to introduce known test signals and investigate the cause of the problems.

In both cases, the investigation pointed to faulty patient leads rather than faults within the ECG machines themselves.

These experiences highlight the importance of diagnostic testing when medical equipment develops a problem, rather than simply waiting for its next scheduled verification.

What Do ECG Patient Leads Actually Do?

ECG patient leads form the connection between the electrodes attached to the patient and the ECG recording equipment.

They carry the small electrical signals detected at the patient's skin to the ECG machine, where those signals are processed and displayed or printed as a waveform.

Depending on the equipment, the patient connection system may include a main patient cable, individual lead wires and electrode connectors.

Over time, these components can experience wear and damage.

Potential problems include:

• Broken or damaged internal conductors.

• Intermittent electrical connections.

• Worn or damaged connectors.

• Cable damage from repeated handling or movement.

• Poor connections between electrodes, leads and the machine.

These faults can affect the quality or reliability of the ECG recording.

How Can Faulty ECG Leads Affect a Recording?

A faulty patient lead may cause an ECG machine to produce an incomplete, unstable or distorted recording.

Depending on the nature of the fault, symptoms may include missing signals, intermittent waveforms, excessive electrical interference or lead-disconnection warnings.

However, not every poor ECG recording indicates a faulty cable.

Incorrect electrode placement, inadequate skin preparation, poor electrode contact, patient movement and electrical interference can also affect ECG recordings.

This is why a systematic approach to troubleshooting is important.

Rather than immediately assuming the ECG machine requires repair or replacement, the equipment and its connections should be assessed to identify the likely cause.

How Does an ECG Signal Simulator Help?

An ECG signal simulator is a specialised test instrument used to generate known electrical waveforms representing cardiac activity.

During performance verification, the simulator provides a controlled signal that can be compared with the ECG machine's recorded output.

Depending on the simulator, ECG machine and testing procedure, this can help assess:

• Whether the equipment detects and reproduces the simulated ECG signal.

• Whether the displayed or printed heart rate corresponds with the selected test signal.

• Whether waveform amplitude and timing are within applicable specifications.

• Whether the recording remains stable.

• Whether patient leads and connections are functioning correctly.

By introducing a known signal, a biomedical technician can investigate whether an abnormal recording is associated with the machine, its patient cable or other components.

This is the approach that helped ClinicCheck identify faulty leads in the two situations described earlier.

Importantly, an ECG simulator does not replace every manufacturer-required performance test. Verification should follow the applicable equipment specifications and test procedures.

Electrical Safety Testing Versus Performance Verification

There's an important distinction between electrical safety testing and functional performance verification.

Electrical Safety Testing

Electrical safety testing assesses relevant electrical safety characteristics of medical equipment.

Depending on the equipment and applicable requirements, this may include protective earth continuity, leakage current measurements and other safety checks.

These tests help identify electrical safety concerns.

Performance Verification

Performance verification assesses whether the equipment performs its intended functions within applicable specifications.

For an ECG machine, this may involve checking its response to known simulated signals, evaluating recorded waveforms and examining the condition and operation of patient leads.

An ECG machine can satisfy its electrical safety requirements while still having a functional problem affecting its recording performance.

This is why the two assessments should not be confused.

What Does AS/NZS 3551 Say About ECG Testing?

AS/NZS 3551:2012 – Management programs for medical equipment provides a framework for the management, maintenance, safety assessment and performance verification of medical equipment.

The standard supports a structured approach to equipment management, including identifying appropriate inspection and verification requirements.

For ECG machines, the specific testing undertaken should take account of the manufacturer's instructions, the equipment's intended use, its condition and the applicable maintenance programme.

At ClinicCheck, ECG performance verification forms part of our biomedical equipment testing activities.

Our experience with faulty ECG leads illustrates the practical value of assessing equipment performance rather than relying solely on whether the machine powers on.

For more information, read our AS/NZS 3551 Explained Knowledge Library guide.

Does an ECG Machine Require a Cardiac Protected Area?

Another question that sometimes arises in medical practices concerns the electrical installation requirements of rooms where ECG machines are used.

AS/NZS 3003:2018 – Electrical installations – Patient areas addresses electrical safety requirements for designated patient areas in healthcare facilities.

However, the presence of an ECG machine does not automatically mean a room must be classified as a cardiac protected area.

The appropriate patient area classification depends on the clinical procedures undertaken, the equipment used and the applicable requirements of the standard.

It is important to distinguish between the electrical safety and performance verification of the ECG machine itself and the electrical installation requirements of the room.

For further information, see our AS/NZS 3003 Explained Knowledge Library guide.

Why Regular ECG Verification Matters

ECG machines are relied upon to provide clinical information, so maintaining their performance is important.

A structured equipment maintenance and verification programme can help identify problems with patient cables, connectors, recording functions and other components before they continue affecting clinical use.

It also provides an opportunity to document the equipment's condition and identify when repairs, replacement parts or further technical investigation may be necessary.

Our two experiences with faulty ECG leads are good examples of why investigating a problem properly matters.

Sometimes the solution isn't replacing the ECG machine. It's identifying the component that's causing the problem.

ECG Machine Testing With ClinicCheck

ClinicCheck, part of NZ Test Group, provides medical equipment electrical safety testing and performance verification for healthcare providers throughout New Zealand.

Our biomedical equipment testing includes ECG machines and a range of other medical devices used in clinical environments.

Whether you're arranging routine equipment verification or have concerns about an ECG machine's performance, appropriate testing can help establish whether the equipment is operating as intended.

Concerned about your ECG machine or patient leads?

Contact ClinicCheck to discuss your medical equipment testing requirements.

This article provides general educational information. ECG equipment should be assessed against the applicable manufacturer's instructions and relevant technical requirements. Clinical decisions and interpretation of ECG recordings remain the responsibility of appropriately qualified healthcare professionals.