Severe hypertrophic cardiomyopathy with left ventricular outflow tract obstruction identified with preprocedural point-of-care ultrasound before emergent tracheal repair

Abstract

A woman in her 60s was brought to the operating room directly from the trauma bay for emergent intervention to repair a tracheal rupture sustained during a reported fall from standing height. She was intubated and sedated prior to arrival by paramedics for respiratory distress. Her family reported that the patient had dizziness after standing followed by the patient fainting and striking her neck. During a preprocedural point-of-care cardiac ultrasound examination, we discovered severe left ventricular hypertrophy with a significantly increased ejection fraction and decreased left ventricular cavity size. This prompted emergent cardiology consultation, which confirmed the presence of severe hypertrophic cardiomyopathy with left ventricular outflow tract obstruction. After a brief delay to optimise her heart rate and volume status, the patient successfully underwent an open reduction and internal fixation of the laryngeal cartilage and was discharged in stable condition with plans to undergo a septal myotomy.

Background

Hypertrophic cardiomyopathy with left ventricular outflow tract obstruction is a rare disease with significant implications for an anaesthesiologist. Using point-of-care ultrasound (POCUS) in an intubated trauma patient, we were able to identify findings concerning for hypertrophic cardiomyopathy, emergently consult the cardiology service for management assistance and ultimately provide a safe anaesthetic for her emergent procedure. This case serves as an important clinical reminder to consider cardiac point-of-care evaluations in patients with known cardiac pathology, in patients where cardiac pathology is in the differential diagnosis and in patients with an unclear medical history where the presence of cardiac pathology could alter the patient management process.

Case presentation

A woman in her 60s was brought to the operating room directly from the trauma bay for emergent intervention to repair a tracheal rupture sustained during a reported fall from standing height. She was intubated by paramedics for respiratory distress prior to arrival with etomidate and rocuronium. Her medical history was reported by her family as consisting of two cerebrovascular accidents and possible atrial fibrillation. Her family also reported that the patient described feeling dizzy prior to fainting and striking her neck on her dresser. No records were immediately available to review as she was visiting from out of town. Upon her presentation to the operating room, the patient’s blood pressure was 142/90 with a heart rate of 72. She was sedated with 50 µg/kg/min of propofol. Review of a chest X-ray, lateral trauma X-ray, and non-contrast head and neck CT scan obtained in the emergency department revealed significant soft tissue emphysema throughout the neck surrounding the laryngeal structures (figures 1–3). Her laboratory results were unremarkable. Her ECG revealed normal sinus rhythm.

Figure 1.

Anteroposterior chest X-ray showing subcutaneous emphysema.

Figure 2.

Lateral cervical spine X-ray.

Figure 3.

Non-contrast head and neck CT scan showing subcutaneous emphysema.

To evaluate for anaesthetically pertinent cardiac pathology leading to her syncopal episode, we performed a POCUS in accordance with the Focus-Assessed Transthoracic Echocardiography (FATE) Protocol in the operating room. We discovered severe left ventricular hypertrophy with a significantly increased ejection fraction and decreased left ventricular cavity size (video 1).^1–3 A cardiologist was emergently summoned to the room while we placed an intra-arterial catheter in the radial artery for constant haemodynamic monitoring. The cardiologist confirmed left ventricular hypertrophy, an ejection fraction of 72.7% by biplane Simpson’s method, a left ventricular outflow tract (LVOT) diameter of 1.88 cm, an LVOT gradient of 104 mm Hg and a pulmonary artery systolic pressure of 43 mm Hg. This qualified her for a diagnosis of hypertrophic cardiomyopathy with left ventricular outflow tract obstruction. All other indices, valvular structures and function were unremarkable.

Video 1. Transthoracic echocardiogram showing subcostal four-chamber view.

bcr-2023-254690supp001.mp4 ^{(668.9KB, mp4)}

DOI: 10.1136/bcr-2023-254690.video01

After discussion with the cardiologist, we decided to target a heart rate range of 55–60 beats/min with a mean arterial pressure (MAP) of 70–80 mm Hg and to provide a 1 L bolus of a balanced crystalloid solution.⁴ After completion of this bolus, we titrated an esmolol infusion to reach our targeted heart rate before gradually inducing general anaesthesia via the existing endotracheal tube with sevoflurane vapour. After an uneventful induction, we turned the patients over to the otolaryngologists who performed an uncomplicated open reduction and internal fixation of the laryngeal cartilage.

After the procedure, the patient was transferred in stable condition from the operating room to the intensive care unit with consultations to the cardiology and cardiothoracic surgery services for management and consideration of possible cardiac intervention.

Outcome and follow-up

After recovering from her tracheal repair, the patient received an automated implantable cardioverter defibrillator and medical optimisation by our cardiologists. She was transferred to a subacute rehabilitation facility where she had improved her functional capacity and continued her medical management. She is scheduled to undergo cardiac septal myotomy on an outpatient basis in 2 months.

Discussion

Hypertrophic obstructive cardiomyopathy (HOCM) is an autosomal dominant disease with variable penetrance characterised by left ventricular hypertrophy in the absence of other diseases which can cause hypertrophy (eg, systemic hypertension, aortic stenosis). This hypertrophy is characterised as disorganised rather than parallel and heterogeneous, which leads to decreased compliance during diastole in nearly all patients as well as varying degrees of an LVOT obstruction. Non-obstructive, latent/labile and obstructive LVOTs show peak pressure gradients less than 30 mm Hg, greater than 30 mm Hg with exertion or greater than 30 mm Hg at rest, respectively. Dynamic obstructive pathology is caused by the Venturi effect, where a rapid flow of blood through a narrowed left ventricular outlet draws the anterior mitral valve closer to the septum and into the LVOT. A variety of situations can worsen the obstruction, including increased myocardial contractility, increased heart rate, decreased preload, decreased afterload and arrhythmias. It is critical to minimise these situations to maintain cardiac output and avoid haemodynamic deterioration.⁵

The long-term management strategies of HOCM are complex and incorporate individual risk stratification and symptomatology. In patients with mild symptomatology and overall low individual risk, lifestyle modifications, such as weight loss, blood pressure control and exercise, are recommended. In patients with moderate LVOT obstruction, beta-blockers or calcium channel blockers, which work to reduce cardiac contractility and LVOT gradients, and myosin inhibitors, which work to directly inhibit cardiac myosin thus lowering LVOT gradients and symptoms, can be administered. In patients with severe LVOT gradients or with symptoms refractory to medications, septal myotomy, myectomy or ethanol ablation can be performed. Patients at risk of sudden cardiac arrest may have automatic implantable cardioverter defibrillators placed. In rare cases, some patients with HOCM may require cardiac transplantation.⁶

The anaesthetic approach in patients with HOCM should consider both the systolic and diastolic components of the disease. A variety of techniques can be used to minimise dynamic obstruction therefore decreasing the likelihood of haemodynamic compromise. Sympathetic stimulation, positive inotropes and positive chronotropes should be avoided as each exacerbates obstruction. Use of phenylephrine or vasopressin allows for increased afterload without altering heart rate or contractility. A slow titration of induction medications as well as pretreatment with phenylephrine to maintain afterload and/or with esmolol to blunt sympathetic response to laryngoscopy can serve to maintain steady haemodynamics and to minimise obstruction. Maintaining sinus rhythm is important to maintain cardiac output in the setting of left ventricular hypertrophy and decreased compliance as these patients are dependent on the atrial kick. If atrial fibrillation does occur, prompt treatment with pharmacological or electric cardioversion should occur. Decreased preload, seen with hypovolaemia as well as high tidal volumes and high peak end-expiratory pressure, accentuates the obstruction, whereas volume overload can lead to pulmonary oedema; therefore, appropriate volume status should be maintained and mechanical ventilation optimised with lower tidal volumes and higher respiratory rate to maintain minute ventilation.⁷

In addition to standard American Society of Anesthesiologists monitoring techniques, an arterial line, a central venous catheter with a pulmonary artery catheter and a transoesophageal echocardiogram (TOE) can be used to monitor haemodynamic changes. Continuous monitoring of blood pressure allows for rapid treatment to maintain afterload with a MAP goal of 65–70 mm Hg for proper subendocardial perfusion in the setting of left ventricular hypertrophy. Pulmonary capillary wedge and central venous pressures can be used to monitor volume status, and TOE can show real-time changes in LVOT obstruction, particularly in high-risk patients.⁵

In this case, POCUS was used to raise the initial concern for the patient’s diagnosis of hypertrophic cardiomyopathy. Developed on the principle of using ultrasound to determine normal versus abnormal findings instead of quantitative findings, POCUS has been used for almost 20 years to make clinical decisions.³ Numerous protocols exist for various clinical situations and patient populations.

Stoll et al reported a two-view approach—apical four chamber and parasternal short axis—to evaluate an elderly patient who presented to their emergency department with undifferentiated syncope. Similar to our patient, the clinicians found severe asymmetric septal wall thickening and significantly decreased left ventricular cavity size and consulted the cardiology service for assistance with further management. Very rapidly, this patient was also formally diagnosed with HOCM.⁸ Although this combination of views was effective in this case, not every patient will have obtainable images in these views alone.³

The FATE protocol, which was used by our team, involves obtaining subcostal four-chamber, apical four-chamber, parasternal long-axis, parasternal short-axis and pleural views.^1–3 The cardiac views can be used to evaluate for the presence of pericardial effusion or tamponade and to determine normal versus abnormal biventricular contractility, relaxation and thickness. It is also possible to visualise significant valvular pathology and alterations suggestive of hypervolaemia or hypovolaemia. With the pleural views, it is possible to rule out pleural effusion and pneumothorax with greater sensitivity and specificity than chest X-rays.⁹

In comparison with a full transthoracic echocardiographic examination performed by a cardiologist, the FATE protocol is extremely fast to perform—typically requiring a trained physician around 1 min to perform a quality scan.³ In the intensive care unit population used for the creation of the protocol, usable images were able to be obtained in 97% of patients.

By using this protocol, we were able to identify HOCM as the likely aetiology of the patient’s fainting episode, which led to her fall and subsequent trauma. We were also able to perform a safe anaesthetic using evidence-based haemodynamic goals and to assist in making the proper referrals to have the patient definitively managed.

Because this protocol is rapid, non-invasive and capable of imparting actionable information, FATE or a similar cardiac assessment should be considered in patients with known cardiac pathology, in patients where cardiac pathology is in the differential diagnosis and in patients with an unclear medical history where the presence of cardiac pathology could alter the patient management process.

Learning points.

• Preprocedural point-of-care ultrasound (POCUS) may identify significant cardiac pathology that can affect the anaesthetic management of a patient.

• POCUS examinations should be considered in patients with known cardiac pathology or in patients where cardiac pathology is in the differential diagnosis.

• The mainstay of hypertrophic obstructive cardiomyopathy (HOCM) management under general anaesthesia consists of maintaining a low heart rate, high afterload and adequate volume status.

• The treatment of HOCM varies based on symptomatology and ranges from lifestyle modification to septal myotomy, myectomy or ethanol ablation.

Ethics statements

Patient consent for publication

Obtained.