A Novel Ultrasound-Based Carotid Plaque Risk Index Associated with the Presence of Cerebrovascular Symptoms

Abstract

Purpose: The purpose of this study was to determine the efficacy of a novel ultrasound-based carotid plaque risk index (CPRI) in predicting the presence of cerebrovascular symptoms in patients with carotid artery stenosis.

Materials and Methods: This was a cross-sectional, observational study involving 56 patients (mean age 76.6 years, 62.5 % male). Plaque grayscale median (GSM) and surface irregularity indices (SII) were measured in 82 stenosed carotid arteries (range 10 – 95 %) and combined with the degree of stenosis (DOS) in the form of (DOS*SII)/(1 + GSM). A reduced index DOS/(1 + GSM) not incorporating plaque surface irregularities was also investigated. Receiver operating characteristic curves (ROC) were used to study the diagnostic efficacy of CPRI, comparing against DOS and an equivalent risk index constructed using a conventional logistic regression based method with model parameters optimized to the dataset (CPRI_logistic).

Results: There were 42 stenosed carotid arteries with cerebrovascular symptoms, and 40 without symptoms. The presence of symptoms significantly correlated with DOS, GSM and SII (p < 0.01). The median CPRI of the symptomatic (asymptomatic) groups were 23.2 (9.2) compared with 0.71 (0.30) for CPRI_logistic (p < 0.01). The diagnostic performance of CPRI exceeded that of CPRI_logistic and DOS, and demonstrated a better separation of the symptomatic and asymptomatic groups.

Conclusion: Our novel risk index combines quantitative measures of carotid plaque echogenicity and surface irregularities with the degree of stenosis. It is a better predictor of cerebrovascular symptoms than the degree of stenosis and could be valuable in studies and clinical trials aimed at identifying vulnerable carotid artery stenoses.

Zusammenfassung

Ziel: Ziel der Studie war die Bestimmung der Leistungsfähigkeit des neuen ultraschallbasierten Karotis-Plaque-Risikoindex (CPRI) zur Vorhersage von zerebrovaskulären Symptomen bei Patienten mit Karotisstenose.

Material und Methoden: Eine Querschnitts-Beobachtungsstudie in 56 Patienten (∅ 76,6 Jahre, 62,5 % ♂). Medianer Grauwert (GSM) der Plaque und Oberflächenunregelmäßigkeits-Indizes (SII) wurden in 82 stenosierten Karotisarterien (Bereich 10 – 95 %) bestimmt und mit dem Stenosegrad (DOS) mittels der Formel (DOS*SII)/(1 + GSM) verbunden. Ein reduzierter Index DOS/(1 + GSM), ohne Berücksichtigung von SII wurde untersucht. „Receiver Operating Characteristic“ (ROC)-Kurven wurden angewandt, um die diagnostische Effizienz des CPRI mit DOS und einem gleichwertigen Risikoindex zu vergleichen, letzterer erstellt mittels einer auf konventionelle logistische Regression basierenden Methode mit für den Datensatz optimierten Modellparametern (CPRI_logistic).

Ergebnisse: 42 Stenosen mit zerebrovaskulären Symptomen und 40 symptomlose Stenosen lagen vor. Das Auftreten von Symptomen korrelierte signifikante mit DOS, GSM und SII (p < 0,01). Der Median des CPRI in den symtomatischen (asymtomatischen) Gruppen betrug 23,2 % (9,2) im Vergleich zu 0,71 (0,30) des CPRI_logistic der symptomatischen (asymtomatischen) Gruppen (p < 0,01). In diagnostischer Leistung war CPRI der CPRI_logistic und dem DOS überlegen und zeigte eine bessere Trennung zwischen symptomatischen und asymptomatischen Gruppen.

Schlussfolgerung: Unser neuer Risikoindex vereinigt die quantitative Messung der Karotisplaque-Echogenität und der Unregelmäßigkeiten der Oberfläche mit dem Grad der Stenose. Es ist ein besserer Prädiktor für zerebrovaskuläre Symptome als der DOS und könnte sich in Untersuchungen und klinischen Studien, die eine Identifizierung vulnerabler Karotisplaques zum Ziel haben, als wertvoll erweisen.

Key words

carotid plaque - risk index - CPRI

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