Case Series of the “Blueberry‐on‐Top" Phenomenon: A Recently Recognized Strain Pattern in Patients With Apical Variant Hypertrophic Cardiomyopathy

BACKGROUND: The "Blueberry-on-Top" phenomenon is a novel echocardiographic strain pattern that has been recently described in patients with apical variant hypertrophic cardiomyopathy (ApHCM). It is identified when there is impaired global longitudinal strain (GLS) with paradoxically advanced time to peak strain (TPS) in a hypertrophied apex with relative sparing of the basal segments. On a standard polar map, GLS will have a pale center while TPS will depict a more robust blue center. OBJECTIVES: While the "Blueberry-on-Top" pattern has been observed in a few prior reports, its true prevalence in patients with ApHCM is currently unknown. We sought to examine the prevalence of this strain pattern among patients with ApHCM. METHODS: A series of patients diagnosed with ApHCM by cardiac MRI were included and compared to a series of normal controls. All patients underwent a standard transthoracic echocardiogram (TTE). For uniform reporting, all echocardiogram studies were post-processed using Tomtec, which is a vendor-independent speckle tracking analysis software. RESULTS: From a cohort of 340 patients with HCM, a total of 15 patients with ApHCM were identified and subsequently compared to 15 normal controls. The "Blueberry-on-Top" pattern was observed in 93% (n = 14) of patients with ApHCM, while none of the normal controls had a "Blueberry-on-Top" pattern. We identified a GLS ratio threshold of 1.26 and a normalized time to peak strain (NTPS) ratio threshold of 0.09. When both thresholds are met, the "Blueberry-on-Top" phenomenon has nearly 100% sensitivity and 93% specificity for the diagnosis of ApHCM. We suggest using these parameters as an adjunctive tool for making the clinical diagnosis of ApHCM and integrating them into a more comprehensive approach. CONCLUSION: The newly recognized "Blueberry-on-Top" strain pattern is unique and can be used as a supportive diagnostic feature in ApHCM.