Imperial College London


Faculty of MedicineNational Heart & Lung Institute

Reader in Cardiac Electrophysiology







South- NHLI Cardiovascular ScienceBlock B Hammersmith HospitalHammersmith Campus





Zachary Whinnett is a Consultant Cardiologist practicing at Imperial College NHS Trust, working principally at Hammersmith and St Mary’s Hospitals. His specialist areas of expertise are pacemakers, implantable defibrillators and cardiac electrophysiology.

His main research interests are in the field of Cardiac resynchronisation therapy. His clinical research program focuses on developing precise and reliable measurement tools to aid in the understanding of the mechanisms through which cardiac resynchronisation therapy provides its beneficial effects. This also allows the identification of areas where this treatment can be improved and allows new innovations in the delivery of this treatment to be reliably and efficiently tested.

He completed his undergraduate training in Medical Sciences at the University of Nottingham and trained as a Junior Doctor on the Barts and the London Medical Rotation.

He moved to Imperial College London to undertake a PhD with Professor Darrel Francis and Professor Jamil Mayet and was awarded a British Heart Foundation Junior Research Fellowship. During his PhD and subsequently he has developed and refined a technique, which allows haemodynamic measurements to made in such as way that they can be reliably used to assess the effects of adjusting pacemaker settings. This technique minimises the effect of spontaneous variations in the haemodynamic measurements, analysis is automated and allows precise and highly reproducible measurements to be obtained.

He completed his clinical speciality training at world leading centres in London and Bordeaux.

Research Programme

Integral to the success of this program is the network of collaborators which he has developed within Imperial College London, as well as nationally and internationally. The members of this network have a wide range of skills and include engineers, world renowned pioneering cardiac device specialists, industry collaborators, statisticians and clinical trial experts.

The clinical experiments flow directly from techniques he has developed and technical skills he has acquired during his research career to date. His clinical work enables him to identify areas where therapy needs to be improved, and provides him with a patient base from which volunteers can be recruited into clinical studies. 

Some of the highlights of the program include the following:

Development of precise and reproducible measurement tools

Prior to embarking on clinical studies, it is critical to ensure that the tools to be used have sufficient precision to reliably answer the clinical question. This has often not been the case in the field cardiac device therapy research.

When used to optimise the settings of biventricular pacemakers commonly used echocardiographic measurements have poor reproducibility.

With Professor Francis and research fellows Dr Graham Cole and Afzal Sohaib and the engineering team of Drs Massoud Zolgharni,  Niti Dhutia and Keith Willson, the group is developing more reliable ways of obtaining echocardiographic measurements for the purpose of device optimisation.  Developing techniques to allow the automation of the analysis of multiple measurements will improve precision by minimising the effect of signal noise.

Similarly commonly used haemodynamic measurements have poor reproducibility when they are used to determine optimal device settings or assess the impact of innovations in the way therapy is delivered. This has also been addressed by developing automated ways to make multiple measurements in order to minimise signal noise.

Conduction disease in heart failure and maximising the potential of Biventricular pacing


Patients with heart failure who have evidence of conduction disease are known to be at increased risk. The pattern of conduction impairment observed in individual patients is variable. However, the impact on heart function of developing particular patterns of conduction impairment is currently not known.

Biventricular pacing therapy aims to treat these conduction defects; however, we do not know how effective current methods for delivering this therapy are at achieving this. As a result we do not know how much room there is for improving the effectiveness of this therapy.

We are using a new tool, which allows detailed maps of the electrical activation pattern of the heart to be recorded rapidly, in conjunction with the precise measures of heart function we have previously developed in order to address these questions.

By using these precise tools we will also test a number of innovations aimed at improving effectiveness of biventricular pacing therapy.

Optimising the settings of Biventricular pacemakers

Biventricular pacemakers are an important treatment for patients with heart failure, the aim is to improve heart function by restoring optimal timings of heart muscle contraction. The settings of the pacemaker can be adjusted in order to fine tune these timings.

We are currently, with the support of the BHF and the National Institute for Health Research, performing a national multicentre randomised clinical outcome study comparing optimisation of these settings using non-invasive haemodynamic measured with high levels of precision against the conventional echocardiographic methods (BRAVO study).

Physiological effects of Biventricular pacing

In order to improve our understanding of the physiological effects of biventricular pacing we are performing invasive studies using precise tools. We have shown that biventricular pacing enhances coronary flow by increasing the diastolic suction wave. We have shown that with therapy myocardial oxygen consumption is increased, rather than decreased as is commonly assumed. However, reassuringly improved cardiac output is achieved by increasing cardiac efficiency.



Butcher CJT, Cantor E, Sohaib A, et al., 2023, Variation in optimal hemodynamic atrio-ventricular delay of biventricular pacing with different endocardial left ventricular lead locations using precision hemodynamics, Journal of Cardiovascular Electrophysiology, Vol:34, ISSN:1045-3873, Pages:1431-1440

Sau A, 2023, Artificial intelligence-enabled electrocardiogram to distinguish atrioventricular re-entrant tachycardia from atrioventricular nodal re-entrant tachycardia, Cardiovascular Digital Health Journal, Vol:4, ISSN:2666-6936, Pages:60-67

Kaza N, Htun V, Miyazawa A, et al., 2023, Upgrading right ventricular pacemakers to biventricular pacing or conduction system pacing: a systematic review and meta-analysis, Europace, Vol:25, ISSN:1099-5129, Pages:1077-1086

Ali N, Arnold AD, Miyazawa AA, et al., 2023, Comparison of methods for delivering cardiac resynchronization therapy: an acute electrical and haemodynamic within-patient comparison of left bundle branch area, His bundle, and biventricular pacing, Ep Europace, Vol:25, ISSN:1099-5129, Pages:1060-1067

Kanagaratnam P, McCready J, Tayebjee M, et al., 2023, Ablation versus anti-arrhythmic therapy for reducing all hospital episodes from recurrent atrial fibrillation: a prospective, randomized, multi-centre, open label trial, Ep Europace, Vol:25, ISSN:1099-5129, Pages:863-872

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