Canadian Cardiovascular Society Clinical Practice Update on Contemporary Management of the Patient With Hypertrophic Cardiomyopathy

Numerous guidelines on the diagnosis and management of hypertrophic cardiomyopathy (HCM) have been published, by learned societies, over the past decade. Although helpful they are often long and less adapted to nonexperts. This writing panel was challenged to produce a document that grew as much from years of practical experience as it did from the peer-reviewed literature. As such, rather than produce yet another set of guidelines, we aim herein to deliver a concentrate of our own experiential learning and distill for the reader the essence of effective and appropriate HCM care. This Clinical Practice Update on HCM is therefore aimed at general cardiologists and other cardiovascular practitioners rather than for HCM specialists. We set the stage with a description of the condition and its clinical presentation, discuss the central importance of "obstruction" and how to look for it, review the role of cardiac magnetic resonance imaging, reflect on the appropriate use of genetic testing, review the treatment options for symptomatic HCM-crucially including cardiac myosin inhibitors, and deal concisely with practical issues surrounding risk assessment for sudden cardiac death, and management of the end-stage HCM patient. Uniquely, we have captured the pediatric experience on our panel to discuss appropriate differences in the management of younger patients with HCM. We ask the reader to remember that this document represents expert consensus opinion rather than dogma and to use their best judgement when dealing with the HCM patient in front of them.

Left Atrial Dysfunction in Apical Hypertrophic Cardiomyopathy: Assessed by Cardiovascular Magnetic Resonance Feature-tracking

PURPOSE

To evaluate the left atrial (LA) function in participants with apical hypertrophic cardiomyopathy (AHCM) by cardiovascular magnetic resonance feature tracking (CMR-FT).

MATERIALS AND METHODS

Thirty typical AHCM (TAHCM) patients, 23 subclinical AHCM (SAHCM) patients and 32 normal healthy volunteers who underwent CMR exam were retrospectively analyzed. LA reservoir, conduit, and contractile function were quantified by volumetric and CMR-FT derived strain and strain rate (SR) parameters from 2-chamber and 4-chamber cine imaging.

RESULTS

Compared with healthy participants, both TAHCM and SAHCM patients had impaired LA reservoir function (total strain [%]: TAHCM 31.3±12.2, SAHCM 31.8±12.3, controls 40.4±10.7, P <0.01; total SR [/s]: TAHCM 1.1±0.4, SAHCM 1.1±0.5, controls 1.4 ± 0.4, P <0.01) and conduit function (passive strain [%]: TAHCM 14.4±7.6, SAHCM 16.4±8.8, controls 23.3±8.1, P <0.01; passive SR [/s]: TAHCM -0.5±0.3, SAHCM -0.6±0.3, controls -1.0±0.4, P <0.01). Regarding contraction function, although TAHCM and SAHCM patients had preserved active emptying fraction and strain (all P >0.05), patients with TAHCM had the lowest active SR value among the 3 groups ( P= 0.03). LA reservoir and conduit strain were both significantly associated with left ventricular mass index and maximal wall thickness (all P <0.05). A moderate correlation between LA passive SR and left ventricular cardiac index ( P <0.01).

CONCLUSIONS

The LA reservoir and conduit function are predominately impaired and appeared in both SAHCM and TAHCM patients.

Apical hypertrophic cardiomyopathy: pathophysiology, diagnosis and management

Since the first description of apical hypertrophic cardiomyopathy (ApHCM) in 1976, contrasting information from all over the world has emerged regarding the natural history of the disease. However, the recommended guidelines on hypertrophic cardiomyopathy (HCM) pay a cursory reference to ApHCM, without ApHCM-specific recommendations to guide the diagnosis and management. In addition, cardiologists may not be aware of certain aspects that are specific to this disease subtype, and a robust understanding of specific disease features can facilitate recognition and timely diagnosis. Therefore, the review covers the incidence, pathogenesis, and characteristics of ApHCM and imaging methods. Echocardiography and cardiovascular magnetic resonance imaging (CMR) are the most commonly used imaging methods. Moreover, this review presents the management strategies of this heterogeneous clinical entity. In this review, we introduce a novel transapical beating-heart septal myectomy procedure for ApHCM patients with a promising short-time result.

Improved Diagnostic Criteria for Apical Hypertrophic Cardiomyopathy

BACKGROUND

There is no acceptable maximum wall thickness (MWT) threshold for diagnosing apical hypertrophic cardiomyopathy (ApHCM), with guidelines referring to ≥15 mm MWT for all hypertrophic cardiomyopathy subtypes. A normal myocardium naturally tapers apically; a fixed diagnostic threshold fails to account for this. Using cardiac magnetic resonance, "relative" ApHCM has been described with typical electrocardiographic features, loss of apical tapering, and cavity obliteration but also with MWT <15 mm.

OBJECTIVES

The authors aimed to define normal apical wall thickness thresholds in healthy subjects and use these to accurately identify ApHCM.

METHODS

The following healthy subjects were recruited: healthy UK Biobank imaging substudy subjects (n = 4,112) and an independent healthy volunteer group (n = 489). A clinically defined disease population of 104 ApHCM subjects was enrolled, with 72 overt (MWT ≥15 mm) and 32 relative (MWT <15 mm but typical electrocardiographic/imaging findings) ApHCM subjects. Cardiac magnetic resonance-derived MWT was measured in 16 segments using a published clinically validated machine learning algorithm. Segmental normal reference ranges were created and indexed (for age, sex, and body surface area), and diagnostic performance was assessed.

RESULTS

In healthy cohorts, there was no clinically significant age-related difference for apical wall thickness. There were sex-related differences, but these were not clinically significant after indexing to body surface area. Therefore, segmental reference ranges for apical hypertrophy required indexing to body surface area only (not age or sex). The upper limit of normal (the largest of the 4 apical segments measured) corresponded to a maximum apical MWT in healthy subjects of 5.2 to 5.6 mm/m2 with an accuracy of 0.94 (the unindexed equivalent being 11 mm). This threshold was categorized as abnormal in 99% (71/72) of overt ApHCM patients, 78% (25/32) of relative ApHCM patients, 3% (122/4,112) of UK Biobank subjects, and 3% (13/489) of healthy volunteers.

CONCLUSIONS

Per-segment indexed apical wall thickness thresholds are highly accurate for detecting apical hypertrophy, providing confidence to the reader to diagnose ApHCM in those not reaching current internationally recognized criteria.

Left ventricular morphologic progression in apical hypertrophic cardiomyopathy

BACKGROUND

Left ventricular (LV) morphologic progression in apical hypertrophic cardiomyopathy (AHC) has not been well studied. We evaluated serial echocardiographic changes in LV morphology.

METHODS

Serial echocardiograms in AHC patients were assessed. LV morphology was categorized according to the presence of an apical pouch or aneurysm, and LV hypertrophic severity and extent; relative, pure, and apical-mid type defined as mild (<15 mm thickness) apical hypertrophy, significant (≥15 mm) apical hypertrophy, and both apical and midventricular hypertrophy, respectively. Adverse clinical events and late gadolinium enhancement (LGE) extent on cardiac magnetic resonance were evaluated for each morphologic type.

RESULTS

In 41 patients, 165 echocardiograms (maximal interval: 4.2 [IQR, 2.3-11.8] years) were evaluated. Morphologic changes were observed in 19 (46%) patients. Eleven (27%) patients displayed the progression of LV hypertrophy toward pure or apical-mid type. Five (12%) and 6 (15%) patients developed new pouches and aneurysms. Patients with progression tended to be younger (50 ± 15.6 vs 59 ± 14.4 years, P = 0.058) and had a longer period of follow-up (12 [5-14] vs 3 [2-4] years, P < 0.001). During a follow-up of 7.6 (IQR 3.0-12.1) years, 21 (51%) experienced clinical events. The relative, pure, and apical-mid types showed different LGE extents (2%, 6%, and 19%, P = 0.004). Patients with severe hypertrophic and apical involvement showed higher clinical event rates.

CONCLUSIONS

About half of AHC patients had a progression of LV morphology to more hypertrophic involvement and/or an apical pouch or aneurysm formation. Advanced AHC morphologic types were associated with higher event rates and scar burdens.

Comparison of cardiovascular magnetic resonance characteristics and clinical prognosis in left ventricular noncompaction patients with and without arrhythmia

BACKGROUND

Left ventricular noncompaction (LVNC) is a rare type of cardiomyopathy, and one of its clinical manifestations is arrhythmia. Cardiovascular magnetic resonance (CMR) is valuable for the diagnosis and prognosis of LVNC. However, studies are lacking on the use of CMR for LVNC patients with arrhythmia. This study aimed to characterize and compare CMR features and prognosis in LVNC patients with and without arrhythmia.

METHODS

Eighty-four LVNC patients diagnosed by CMR were enrolled retrospectively in this study. Clinical data, arrhythmia characteristics, and CMR parameters were collected. Patients were divided into different groups according to the arrhythmia characteristics and CMR manifestations for statistical analysis and comparison. Ventricular tachycardia (VT), ventricular fibrillation (Vf), ventricular flutter (VFL), III° atrioventricular block (III° AVB), Wolff-Parkinson-White syndrome (WPW) and ventricular escape (VE) were defined as malignant arrhythmias and benign arrhythmias included premature ventricular contraction, atrial premature beats, atrial fibrillation, supraventricular tachycardia, supraventricular premature beat, bundle branch block, atrial flutter and sinus tachycardia. The outcome events were defined as a composition event of cardiac death, rehospitalization for heart failure, heart transplantation, and implantation of an implantable cardioverter defibrillator (ICD).

RESULTS

Sixty-seven LVNC patients (79.76%) mainly presented with arrhythmia, including premature ventricular beat (33 patients [27.73%]), bundle branch block (14 patients [11.77%]), electrocardiogram waveform changes (18 patients [15.13%]), and ventricular tachycardia (11 patients [9.24%]). The cardiac function and structure parameters had no significant difference among the nonarrhythmia group, benign arrhythmia group, and malignant arrhythmia group. However, the presence of late gadolinium enhancement (LGE) was higher in the malignant arrhythmia group than in the other two groups (p = 0.023). At a mean follow-up of 46 months, cardiac events occurred in twenty-three patients (46.94%). Kaplan-Meier analysis showed that there was no statistically significant difference in prognosis among the nonarrhythmia, benign, and malignant arrhythmia groups, but the patients with arrhythmia and association with LGE + or left ventricular ejection fraction (LVEF) < 30% had a higher risk than patients with LGE- or LVEF > 30% (LGE +, HR = 4.035, 95% CI 1.475-11.035; LVEF < 30%, HR = 8.131, 95% CI 1.805-36.636; P < 0.05).

CONCLUSIONS

In LVNC patients, the types of arrhythmias are numerous and unrepresentative, and arrhythmia is not the prognostic factor. Arrhythmia combined with presence of LGE or LVEF < 30% is associated with poor prognosis in LVNC patients.

Patients who do not fulfill criteria for hypertrophic cardiomyopathy but have unexplained giant T-wave inversion: a cardiovascular magnetic resonance mid-term follow-up study

BACKGROUND

Patients who have unexplained giant T-wave inversions but do not meet criteria for hypertrophic cardiomyopathy (HCM) (left ventricular (LV) wall thickness < 1.5 cm) demonstrate LV apical morphological features that differ from healthy subjects. Currently, it remains unknown how the abnormal LV apical morphology in this patient population changes over time. The purpose of this study was to investigate LV morphological and functional changes in these patients using a mid-term cardiovascular magnetic resonance (CMR) exam.

METHODS

Seventy-one patients with unexplained giant T-wave inversion who did not fulfill HCM criteria were studied. The mean interval time of the follow-up CMR was 24.4 ± 8.3 months. The LV wall thickness was measured in each LV segment according to the American Heart Association 17-segmented model. The apical angle (ApA) was also measured. A receiver operating curve (ROC) was used to identify the predictive values of the CMR variables.

RESULTS

Of 71 patients, 16 (22.5%) progressed to typical apical HCM, while 55 (77.5%) did not progress to HCM criteria. The mean apical wall thickness was significantly different between the two groups at both baseline and follow-up, with the apical HCM group having greater wall thickness at both time points (all p < 0.001). There was a significant difference between the two groups in the change of ApA (- 1.5 ± 2.7°/yr vs. - 0.7 ± 2.0°/yr, p < 0.001) over time. The combination of mean apical wall thickness and ApA proved to be the best predictor for fulfilling criteria for apical HCM with a threshold value of 8.1 mm and 90° (sensitivity 93.8%, specificity 85.5%).

CONCLUSIONS

CMR metrics identify predictors for progression to HCM in patients with unexplained giant T-wave inversion.

Apical hypertrophic cardiomyopathy with left ventricular apical aneurysm: prevalence, cardiac magnetic resonance characteristics, and prognosis

Aims

Hypertrophic cardiomyopathy (HCM) with left ventricular apical aneurysm (LVAA) is associated with an increased risk of adverse cardiovascular events. However, the clinical significance of LVAA in apical HCM (ApHCM) has not been reported. This study aimed to investigate the prevalence, cardiac magnetic resonance (CMR) characteristics, and prognosis of LVAA in ApHCM patients.

Methods and results

A total of 1332 consecutive ApHCM patients confirmed by CMR in our hospital were retrospectively analysed. LVAAs were identified in 31 patients of all ApHCM patients (2.3%, 31/1332). Besides, 31 age- and gender-matched ApHCM patients without LVAA were used for comparison. Of the 31 aneurysm patients (mean age, 53.8 ± 15.1 years old), 28 (90.3%) had clinical symptoms, and 3 (9.7%) had a family history of HCM. The rate of missed diagnosis of echocardiography for detecting LVAA was 64.5% (20/31), most (90%, 18/20) of unidentified LVAAs by echocardiography were small aneurysms (&lt;20 mm). Compared with ApHCM patients without LVAA, the proportion of systolic mid-cavity obstruction and late gadolinium enhancement (LGE) presence, and the LGE extent in ApHCM patients with LVAA were significantly higher (all P&lt;0.05). The Kaplan–Meier curves showed that the event-free survival rate in ApHCM patients with LVAA was significantly lower than that in ApHCM patients without LVAA (log rank, P = 0.010).

Conclusion

ApHCM with LVAA is a very rare condition, which is often missed by echocardiography and could be reliably detected with CMR and is associated with a higher risk of adverse cardiovascular events compared with ApHCM without LVAA.

CMR publications from China of the last more than 30 years

Cardiovascular magnetic resonance (CMR) is a non-invasive imaging technology, gradually playing an irreplaceable role in the diagnosis and treatment of cardiovascular diseases. This review demonstrates the progress and research highlights of Chinese CMR publications of the last more than 30 years. At initial stage (1988 to 1997), CMR was introduced to evaluate cardiac anatomy, blood flow and ventricular function roughly in China. In the development stage (1998-2007), CMR began to play an important role in the diagnosis of cardiovascular and pericardial disease with the emergence of new techniques, such as myocardial perfusion imaging and magnetic resonance angiography. Since 2008, the development of CMR in China has reached a prosperous period. Cardiovascular disease can be both qualitatively and quantitatively assessment by CMR "one-stop" multi-parameter imaging, including the morphology, function, myocardial perfusion, tissue characteristics, metabolism and even the microstructure of myocardial fibers, which provides comprehensive assessment of the severity, risk stratification and prognosis of cardiovascular disease. Although CMR in China developed very rapidly in recent years, China still needs to put more efforts in CMR research and make greater contributions to the development of CMR in the world.

Revisiting the prevalence and diversity of localized thinning of the left ventricular apex

BACKGROUND

The left ventricular apex commonly has a paper-thin structure. However, available data about its structure are limited to variable samples, methodologies, and results.

OBJECTIVE

To investigate the structural anatomy of the left ventricular apex using living heart datasets with the latest computed tomography scanner.

METHODS

One hundred thirty-one consecutive patients (median age, 73 years; 58% men) who underwent cardiac computed tomography were retrospectively analyzed. Patients with severe aortic stenosis were analyzed separately. Thickness and diameters of the thinnest part of the left ventricular apex during mid-diastole were measured using orthogonal multiplanar reconstruction images. The area of thinning was estimated using the formula for the ellipse.

RESULTS

In 88 patients without severe aortic stenosis, the median thickness of the thinnest area of the left ventricular apex was only 0.9 mm. Among them, 74%, 99%, and 100% of cases displayed a left ventricular apex thinner than 1.0, 3.0, and 5.0 mm, respectively. The median area of the thinnest region was 5.6 mm² . In 43 patients with severe aortic stenosis, the median thickness of the thinnest area of the left ventricular apex was 1.2 mm. Among them, 51%, 93%, and 100% of cases displayed a left ventricular apex thinner than 1.0, 3.0, and 5.0 mm, respectively. The median area of the thinnest region was 3.9 mm² .

CONCLUSIONS

Localized thinning of the left ventricular apex is unexceptional, regardless of aortic stenosis with concentric left ventricular hypertrophy, thus highlighting the need for a reappreciation of this feature to avoid inadvertent catastrophic complications.

Development and validation of a new method to diagnose apical hypertrophic cardiomyopathy by gated single-photon emission computed tomography myocardial perfusion imaging

AIM

The aim of this study is to develop and validate a new method to diagnose apical hypertrophic cardiomyopathy (AHCM) by the integral quantitative analysis of myocardial perfusion and wall thickening from gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI).

PATIENTS AND METHODS

Twenty-two consecutive patients, who showed T wave inversion of at least 3 mm in precordial leads and sinus rhythm in ECG, were enrolled. All the patients underwent cardiac magnetic resonance (CMR), gated rest SPECT MPI and echocardiography. According to CMR diagnostic results, 13 patients were categorized as in the AHCM group and the remaining nine patients were categorized as in the non-AHCM group. Operators who were blinded to the CMR diagnosis independently performed the diagnosis by gated SPECT MPI. The regions of interest inside the apical hotspots on the perfusion polar map were drawn and the mean values of wall thickening in the drawn region of interests were calculated. Using MRI diagnosis as the gold standard, AHCM was diagnosed based on receiver operating characteristic analysis of the mean wall thickening in the apical perfusion hotspot. The area under curve, sensitivity, specificity, and accuracy of our method were 0.97, 100%, 89%, and 95%, respectively.

CONCLUSION

Our new method has high sensitivity, specificity, and accuracy against CMR diagnosis. It has great promise to become a clinical tool in the diagnosis of AHCM.