Date: September 27, 2024
Perioperative echocardiography has revolutionised our approach to patient care in the surgical setting. As an expert user of critical care ultrasound, I've witnessed first-hand the transformative impact of this technology on patient outcomes in UK hospitals. This comprehensive guide aims to demystify perioperative echocardiography, taking you on a journey from foundational principles to more advanced techniques.
The evolution of perioperative echocardiography in the UK has been remarkable. From its initial use in cardiac surgery, it has now become an indispensable tool across various surgical specialties.
In this guide, we'll explore the fundamental concepts, essential measurements, and advanced applications of perioperative echocardiography. Whether you're an anaesthetist, intensivist, or surgeon, this resource will enhance your understanding and application of this vital skill.
Understanding the Basics of Perioperative Echocardiography
Perioperative echocardiography, at its core, is the application of ultrasound technology to visualise and assess cardiac structure and function in the context of surgical care. This powerful diagnostic tool utilises high-frequency sound waves to create real-time images of the heart, providing invaluable insights into a patient's cardiovascular status.
In the perioperative setting, we primarily employ two types of echocardiography: transthoracic echocardiography (TTE) and transoesophageal echocardiography (TOE). TTE, performed by placing a transducer on the chest wall, offers a non-invasive approach suitable for preoperative and postoperative assessments. TOE, involving the insertion of a probe into the oesophagus, provides superior image quality and is particularly useful during cardiac and major non-cardiac surgeries.
The physics underlying echocardiography is fascinating. Ultrasound waves, typically in the range of 2-15 MHz, are emitted from piezoelectric crystals in the transducer. These waves interact with tissues of varying densities, resulting in reflections that are captured and processed to form images. Understanding these principles is crucial for optimising image acquisition and interpretation.
Mastery of standard echocardiographic views forms the foundation of competent practice. The parasternal long-axis view, for instance, offers an excellent assessment of left ventricular size and function, as well as evaluation of the mitral and aortic valves. The apical four-chamber view provides insights into both ventricular and atrial chambers, while the subcostal view is particularly useful in critically ill patients where other acoustic windows may be challenging.
Each view holds clinical significance in the perioperative period. For example, the parasternal short-axis view at the level of the papillary muscles is invaluable for assessing regional wall motion abnormalities, which could indicate myocardial ischaemia during surgery. The ability to obtain and interpret these views efficiently can significantly impact intraoperative decision-making and patient management.
As we progress through this guide, we'll build upon these fundamental concepts, exploring how they inform more advanced techniques and measurements in perioperative echocardiography.
Essential Equipment and Setup for Perioperative Echocardiography
Selecting the appropriate ultrasound machine for perioperative use is a critical decision that can significantly impact the quality of patient care. In the UK, where NHS budgets are often constrained, it's essential to balance functionality with cost-effectiveness. High-end systems like the GE Vivid E95 offer exceptional image quality and advanced features but may be more suitable for dedicated echocardiography labs. For routine perioperative use, mid-range portable systems such as the Philips CX50 or the Sonosite X-Porte provide an excellent compromise between functionality and portability.
Transducer selection is equally crucial. For transthoracic echocardiography (TTE), a phased array probe (typically 2-4 MHz) is the workhorse, offering good penetration and a small footprint ideal for intercostal scanning. For transoesophageal echocardiography (TOE), multiplane probes capable of 0-180 degree rotation are standard in the UK. It's vital to handle these expensive probes with care, following manufacturer guidelines for cleaning and storage to ensure longevity and optimal performance.
Optimising image quality is an art that combines technical knowledge with practical skills. Start by adjusting the depth to ensure the structure of interest fills most of the screen. Fine-tune the gain to achieve a balance between image clarity and noise reduction. Frequency adjustment can help balance penetration (lower frequencies) with resolution (higher frequencies). Time-gain compensation (TGC) sliders allow for depth-specific gain adjustments, particularly useful in challenging acoustic windows.
In the UK theatre environment, infection control is paramount. Follow local trust guidelines for cleaning and disinfecting equipment. For TTE, use single-use gel packets rather than large bottles to minimise cross-contamination risks. With TOE, meticulous cleaning and high-level disinfection between patients are essential. Some UK centres have adopted single-use TOE probe covers as an additional safety measure.
When setting up for a perioperative echocardiography examination, consider the ergonomics of the environment. Position the ultrasound machine to allow simultaneous viewing of the echo images and the patient's face and monitors. In cardiac theatres, coordinate with perfusionists and surgeons to ensure the echo setup doesn't interfere with their equipment or access to the patient.
Lastly, don't underestimate the importance of archiving images and measurements. Many UK hospitals now integrate echo machines with PACS (Picture Archiving and Communication System), allowing for seamless documentation and facilitating multidisciplinary discussions. Familiarise yourself with your institution's archiving protocols to ensure all relevant images and clips are stored for future reference and quality assurance.
By mastering the essentials of equipment selection and setup, you'll be well-prepared to perform high-quality perioperative echocardiography, enhancing patient safety and surgical outcomes in your practice.
Fundamental Measurements and Calculations in Perioperative Echocardiography
Accurate quantification is the cornerstone of perioperative echocardiography, providing objective data to guide clinical decision-making. Let's explore the key measurements and calculations that form the basis of a comprehensive echo assessment.
Left ventricular systolic function is perhaps the most crucial parameter in perioperative risk stratification. The left ventricular ejection fraction (LVEF) remains the most widely used measure, despite its limitations. In the UK, we typically employ the biplane Simpson's method, measuring end-diastolic and end-systolic volumes in the apical 4-chamber and 2-chamber views. A normal LVEF is considered >55%, with 45-54% suggesting mild dysfunction, 30-44% moderate, and <30% severe. However, remember that LVEF is load-dependent and may not always reflect contractility accurately.
Diastolic function evaluation has gained increasing recognition in perioperative care. The European Association of Cardiovascular Imaging (EACVI) recommends a stepwise approach. Start by assessing mitral inflow patterns (E and A waves), then measure e' velocity at the mitral annulus using tissue Doppler. The E/e' ratio provides an estimate of left atrial pressure, with a value >14 suggesting elevated pressures. Additional parameters include left atrial volume index and tricuspid regurgitation velocity.
Valvular function analysis is critical, particularly in an ageing UK population with a high prevalence of degenerative valve disease. For stenotic lesions, measure the mean gradient and valve area (continuity equation for aortic stenosis, pressure half-time for mitral stenosis). Regurgitant lesions require assessment of the vena contracta width, effective regurgitant orifice area (EROA), and regurgitant volume. The severity of valve disease can significantly impact anaesthetic management and surgical risk.
Right ventricular (RV) function assessment has historically been challenging due to the chamber's complex geometry. The tricuspid annular plane systolic excursion (TAPSE) offers a simple measure of longitudinal RV function, with values <17mm indicating dysfunction. RV fractional area change (FAC) provides a more comprehensive assessment, with values <35% suggesting RV systolic dysfunction. In the perioperative setting, RV function can be particularly important in patients with pulmonary hypertension or undergoing lung resection.
Estimating cardiac output and stroke volume adds valuable haemodynamic data to your assessment. The most common method in perioperative echocardiography is the left ventricular outflow tract (LVOT) Doppler technique. Measure the LVOT diameter in the parasternal long-axis view and the LVOT velocity-time integral (VTI) using pulsed-wave Doppler in the apical 5-chamber view. Stroke volume is calculated as π(LVOT diameter/2)² × LVOT VTI, and cardiac output is stroke volume × heart rate.
Remember, these measurements should not be interpreted in isolation but integrated with clinical context and other monitoring data. Regular practice and participation in quality assurance programmes, such as those offered by the British Society of Echocardiography (BSE), are essential for maintaining accuracy and reliability in your measurements.
Perioperative Echocardiography in Non-Cardiac Surgery
The application of echocardiography in non-cardiac surgery has grown exponentially in recent years, reflecting its value in risk stratification and perioperative management. In the UK, where an ageing population often presents with multiple comorbidities, this tool has become indispensable for many anaesthetists and surgeons.
Preoperative cardiac risk stratification is a key application of echocardiography in non-cardiac surgery. The National Institute for Health and Care Excellence (NICE) recommends considering preoperative echocardiography for patients with suspected moderate or severe valvular heart disease, or for those with unexplained dyspnoea. In my practice, I find it particularly useful in patients with poor functional capacity or equivocal stress test results.
A focused preoperative echo can provide crucial information on left ventricular function, valvular disease, right ventricular function, and volume status. For instance, identifying a patient with moderate aortic stenosis may alter the anaesthetic plan, favouring a technique that maintains systemic vascular resistance and avoids tachycardia.
Intraoperatively, echocardiography can be a game-changer in managing haemodynamic instability. In major abdominal or orthopaedic surgeries, unexplained hypotension can be swiftly assessed using a focused TTE or TOE examination. Is it due to hypovolaemia, ventricular dysfunction, or other causes like pulmonary embolism? This real-time information allows for targeted interventions, potentially avoiding the need for blind fluid challenges or empirical vasopressor therapy.
Moreover, intraoperative echocardiography can guide fluid management, a contentious issue in perioperative care. By assessing inferior vena cava dynamics or performing a passive leg raise test with echo, we can predict fluid responsiveness more accurately than with static parameters alone.
Postoperatively, echocardiography plays a vital role in detecting and managing complications. Using an example from my registrar training, where a patient developed acute dyspnoea following hip arthroplasty. A bedside TTE revealed severe left ventricular systolic dysfunction, likely due to perioperative myocardial infarction, guiding our management towards early coronary intervention.
There is a lack of objective evidence from randomised controlled trials (RCT) on the impact of preoperative echocardiography on perioperative outcomes. However, that said, it may provide valuable data in certain clinical scenarios, such as major abdominal surgery (including liver transplantation), extensive vascular surgery and surgery where significant haemodynamic instability is anticipated. There is a large multicentre RCT currently ongoing in South Korea. This study aims to evaluate the benefit of perioperative echocardiography in predicting cardiovascular events in non cardiac surgery. Keep your eyes peeled for the final results!
Advanced Techniques in Perioperative Echocardiography
As perioperative echocardiography continues to evolve, advanced techniques are increasingly finding their way into routine practice, offering new insights into cardiac structure and function. These methods, while complex, can provide invaluable information in challenging clinical scenarios.
3D echocardiography has emerged as a powerful tool in the perioperative setting. Unlike traditional 2D imaging, 3D echo provides a comprehensive view of cardiac structures, particularly useful for valvular assessment. In the UK, where mitral valve repair is increasingly performed, 3D TOE has become instrumental in guiding surgical technique and assessing immediate post-repair results. The ability to visualise the entire mitral apparatus in a single view allows for precise localisation of pathology and evaluation of repair adequacy.
Strain imaging, particularly global longitudinal strain (GLS), represents a significant advance in the assessment of myocardial function. This technique measures myocardial deformation and can detect subtle changes in contractility before a decline in ejection fraction becomes apparent. In the perioperative context, strain imaging can be particularly useful in patients receiving cardiotoxic chemotherapy prior to surgery. A reduction in GLS may indicate subclinical left ventricular dysfunction, prompting closer monitoring or alteration of the anaesthetic plan.
Contrast-enhanced echocardiography has found its niche in specific perioperative scenarios. By injecting microbubble contrast agents, we can enhance endocardial border definition, crucial for accurate assessment of regional wall motion abnormalities. This technique is particularly valuable in critically ill patients with poor acoustic windows. Moreover, contrast echocardiography can help in the diagnosis of intracardiac shunts, which may have significant implications for intraoperative management, especially in neurosurgery where paradoxical air embolism is a concern.
Stress echocardiography for preoperative risk stratification deserves special mention. While not routinely used in all patients, it can provide valuable information in intermediate-risk patients undergoing major surgery. The choice between exercise and pharmacological stress (usually dobutamine in the UK) depends on the patient's ability to exercise and local expertise. Stress echo can unmask significant coronary artery disease and provide information on myocardial viability and contractile reserve.
It's worth noting that these advanced techniques require specific training and expertise. In the UK, the British Society of Echocardiography (BSE) offers accreditation in advanced echocardiography techniques, which I would strongly recommend for those looking to incorporate these methods into their practice.
As we push the boundaries of perioperative echocardiography, it's crucial to remember that advanced techniques should complement, not replace, fundamental assessments. The integration of these methods into clinical practice should be guided by their ability to influence patient management and improve outcomes. As perioperative echocardiographers, our challenge is to judiciously apply these powerful tools to enhance patient care in the dynamic and often high-pressure environment of the operating theatre.
Transoesophageal Echocardiography (TOE) in Perioperative Care
Transoesophageal echocardiography (TOE) has revolutionised perioperative cardiac imaging, offering unparalleled views of cardiac structures and great vessels. In the UK, where I've had the privilege of working in several major cardiac centres, TOE has become an integral part of cardiac surgery and is increasingly used in complex non-cardiac procedures.
The indications for perioperative TOE are numerous and evolving. In cardiac surgery, it's almost universally used for pre-pump evaluation, de-airing procedures, and post-repair assessment. In non-cardiac surgery, common indications include monitoring for myocardial ischaemia in high-risk patients, evaluating unexplained haemodynamic instability, and assessing for suspected acute aortic syndromes.
Before considering TOE, it's crucial to review contraindications. Absolute contraindications include oesophageal strictures, tumours, or recent surgery. Relative contraindications, such as severe cervical spine disease or coagulopathy, require careful risk-benefit analysis. In the UK, we follow the BSE guidelines for TOE use, which provide comprehensive advice on indications and safety considerations.
Probe insertion and manipulation techniques require skill and practice. After induction of anaesthesia and endotracheal intubation, the probe is typically inserted under direct laryngoscopy guidance. Gentle, steady pressure usually allows smooth passage into the oesophagus. Once inserted, the probe can be manipulated through a combination of advancement/withdrawal, rotation, and flexion/anteflexion. Mastery of these manoeuvres is essential for obtaining optimal views.
Key TOE views form the basis of a comprehensive examination. The mid-oesophageal four-chamber view provides an excellent assessment of biventricular function and volume status. The transgastric short-axis view at the mid-papillary level is ideal for assessing regional wall motion abnormalities and global left ventricular function. The mid-oesophageal long-axis view offers detailed evaluation of the left ventricular outflow tract, aortic valve, and proximal ascending aorta.
TOE-guided interventions have become increasingly common in UK cardiac theatres. In mitral valve repair, TOE plays a crucial role in assessing the mechanism of regurgitation and guiding the surgical approach. Post-repair, immediate TOE evaluation can detect residual regurgitation or iatrogenic stenosis, allowing for prompt revision if necessary. Similarly, in aortic valve procedures, TOE helps in sizing prosthetic valves and detecting paravalvular leaks.
In non-cardiac surgery, TOE can guide interventions such as vena cava filter placement or intra-aortic balloon pump insertion. It's also invaluable in managing perioperative aortic emergencies, providing real-time imaging to guide surgical or endovascular interventions.
As perioperative echocardiographers, we must remember that TOE is an invasive procedure with potential complications. Oesophageal perforation, whilst rare, is a serious risk. Dental damage can occur during probe insertion. Constant vigilance and gentle technique are essential to minimise these risks.
The future of perioperative TOE in the UK looks promising, with ongoing research into its cost-effectiveness and impact on patient outcomes. As we continue to refine our skills and expand its applications, TOE will undoubtedly remain a cornerstone of advanced perioperative cardiac imaging.
Echocardiographic Assessment of Specific Cardiac Conditions
In perioperative care, we frequently encounter patients with pre-existing cardiac conditions that require special consideration. Echocardiography plays a pivotal role in assessing these conditions and guiding perioperative management.
Valvular heart disease is particularly prevalent in the UK's ageing population. In aortic stenosis, a common finding in elderly surgical patients, echocardiography allows us to quantify severity through measurement of valve area and mean gradient. The low-flow, low-gradient variant can be particularly challenging, often requiring dobutamine stress echocardiography for accurate assessment. For mitral regurgitation, careful evaluation of the mechanism (primary vs. secondary) and quantification of severity using parameters like vena contracta width and effective regurgitant orifice area (EROA) are crucial for risk stratification.
Cardiomyopathies present unique challenges in the perioperative period. In hypertrophic cardiomyopathy, echocardiography helps assess the degree of left ventricular outflow tract obstruction and systolic anterior motion of the mitral valve, guiding anaesthetic management to avoid hypotension and tachycardia. Dilated cardiomyopathy requires careful evaluation of biventricular function and optimization of loading conditions. The role of strain imaging is growing in this context, often detecting subclinical dysfunction before changes in ejection fraction become apparent.
Pericardial diseases can significantly impact haemodynamics during surgery. Echocardiography is the gold standard for diagnosing pericardial effusion and assessing for signs of tamponade, such as right atrial or right ventricular diastolic collapse. In constrictive pericarditis, tissue Doppler imaging of the mitral annulus and evaluation of respirophasic variation in mitral inflow velocities can help differentiate it from restrictive cardiomyopathy.
Intracardiac masses and devices are increasingly common findings in our ageing and medically complex patient population. Echocardiography, particularly TOE, excels in characterising intracardiac masses, differentiating between thrombi, vegetations, and tumours. For patients with mechanical circulatory support devices, such as left ventricular assist devices (LVADs), echocardiography is crucial for assessing device function, detecting complications like thrombosis, and guiding device settings.
In all these conditions, a systematic approach to echocardiographic assessment, combined with integration of clinical and other investigative findings, is key to providing optimal perioperative care.
Haemodynamic Assessment and Fluid Management
Echocardiography has transformed our approach to haemodynamic assessment and fluid management in the perioperative period. In the UK, where there's increasing emphasis on individualised patient care, echo-guided haemodynamic management has become a valuable tool in our armamentarium.
Echocardiographic evaluation of volume status begins with assessment of the inferior vena cava (IVC). IVC diameter and distensibility index provide ‘some’ insights into right atrial pressure and fluid tolerance. However, it's crucial to interpret these findings in the context of right ventricular function and positive pressure ventilation. In mechanically ventilated patients, superior vena cava assessment using TOE can be more reliable.
Guiding fluid therapy is perhaps one of the most common applications of perioperative echocardiography. The concept of fluid responsiveness – a significant increase in stroke volume in response to fluid administration – can be assessed using various echo techniques. The passive leg raise test, combined with measurement of left ventricular outflow tract (LVOT) velocity time integral (VTI), offers a non-invasive method to predict fluid responsiveness. An increase in LVOT VTI >12% during leg raise suggests fluid responsiveness.
Echocardiography also guides vasopressor use by providing insights into the underlying cause of hypotension. Is it due to vasodilation, cardiac dysfunction, or hypovolaemia? The answer to this question, readily provided by a focused echo, can guide the choice between fluid boluses, inotropes, or vasopressors.
Assessing response to interventions is another key strength of perioperative echocardiography. Real-time imaging allows us to observe changes in ventricular filling, contractility, and valvular function in response to fluid challenges or vasoactive medications. This immediate feedback enables rapid titration and optimisation of therapy.
Integration with other monitoring techniques is crucial for comprehensive haemodynamic assessment. While echocardiography provides valuable snapshots, continuous monitors like arterial lines and cardiac output monitors offer trending data. The combination of these modalities, interpreted in the context of clinical findings, allows for nuanced and personalised haemodynamic management.
As we continue to refine our approach to perioperative fluid management, echocardiography will undoubtedly play an increasingly central role, helping us move towards truly individualised and physiology-based patient care.
Training and Certification in Perioperative Echocardiography
In the UK, the landscape of perioperative echocardiography training has evolved significantly over the past decade. As the use of this modality has expanded beyond cardiothoracic anaesthesia, there's been a growing recognition of the need for structured training pathways and formal certification processes.
The primary route for UK anaesthetists to gain accreditation in transthoracic echocardiography (TTE) is through the Focused Ultrasound in Intensive Care Echo (FUSIC) accreditation, offered by the Intensive Care Society (ICS). This pathway involves a combination of theoretical learning, hands-on training, and logbook completion. Candidates must perform and report on 50 cases, followed by a triggered assessment. While initially designed for intensive care, FUSIC Heart has become popular among anaesthetists for its focused, clinically relevant approach.
For those specialising in cardiac anaesthesia, transoesophageal echocardiography (TOE) accreditation is often pursued through the British Society of Echocardiography accreditation process. This involves completion of a logbook of 125 cases, a written examination, and a practical assessment. The European Association of Cardiovascular Imaging (EACVI) also offers TOE certification, which is recognised in the UK and provides a pathway for those interested in a broader European qualification.
Continuing professional development is crucial in this rapidly evolving field. The BSE, EACVI and various NHS trusts offer regular workshops, webinars, and conferences. Many UK centres have implemented regular echo meetings, where challenging cases are discussed, providing valuable learning opportunities.
Establishing a perioperative echocardiography service in your NHS Trust requires careful planning and often a business case demonstrating cost-effectiveness and potential improvements in patient outcomes. Key considerations include equipment procurement, training of personnel, development of protocols, and integration with existing perioperative pathways. Collaboration with cardiology departments can be valuable, potentially sharing resources and expertise.
As perioperative echocardiography continues to grow in importance, it's likely that we'll see further developments in training pathways and accreditation processes. There's ongoing discussion about incorporating basic echo skills into the anaesthesia curriculum, reflecting its increasing role as a core skill for anaesthetists. Whatever the future holds, maintaining high standards of training and practice will be crucial to ensuring the safe and effective use of this powerful diagnostic tool.
Conclusion
As we conclude this comprehensive guide to perioperative echocardiography, it's clear that this modality has become an indispensable tool in modern perioperative care. From basic principles to advanced techniques, echocardiography offers unparalleled insights into cardiac structure and function, guiding clinical decision-making at every stage of the perioperative journey.
The impact of perioperative echocardiography on patient outcomes cannot be overstated. By allowing real-time assessment of cardiac function and haemodynamics, it enables us to tailor our anaesthetic and surgical approaches to individual patient physiology. Whether it's guiding fluid management in major abdominal surgery, assessing repair adequacy in mitral valve procedures, or managing acute haemodynamic instability, echocardiography has transformed our ability to provide personalised, physiology-based care.
As we look to the future, the field of perioperative echocardiography continues to evolve at a rapid pace. Emerging technologies like AI-assisted interpretation and handled devices promise to further enhance our diagnostic capabilities and expand access to this valuable tool. However, as we embrace these innovations, it's crucial that we maintain our focus on clinical relevance and patient-centred care.
For those embarking on their journey in perioperative echocardiography, I encourage you to pursue formal training and accreditation. The learning curve can be steep, but the rewards – in terms of enhanced patient care and professional satisfaction – are immense. Remember that becoming proficient in echocardiography is a continuous process, requiring ongoing practice, reflection, and learning.
To my colleagues already versed in this field, I urge you to continue pushing the boundaries of what's possible with perioperative echocardiography. Engage in research, share your knowledge with others, and always strive to integrate your echo findings with clinical context and other available data.
Perioperative echocardiography is more than just a diagnostic tool – it's a window into the dynamic physiology of our patients. By mastering this skill, we equip ourselves to provide truly outstanding perioperative care, tailored to each individual patient's needs. As we continue to advance in this field, I'm excited to see how perioperative echocardiography will further transform our practice and improve outcomes for our patients.
About the Writer
Dr Rachel Wong is an consultant intensivist-anaesthetist currently based at the Royal Papworth Hospital, Cambridge, UK. She is passionate about all things related to ultrasound, more specifically Transoesophgeal Echocardiography.
Follow Rachel on Twitter/X for more educational content: https://x.com/RachelWongLiene
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