Cardiac resynchronisation therapy

 

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Summary

Aim: Cardiac resynchronisation therapy (CRT) has been shown to improve haemodynamics and clinical symptoms in heart failure patients. The present study evaluated the effects of a 4-month CRT on myocardial blood flow (MBF) at rest, after vasodilation and on myocardial oxygen consumption (MVO₂). Patients, Methods: We studied 16 patients with idiopathic dilated cardiomyopathy prior to and during CRT performed as biventricular pacing. Resting MBF and MVO₂ were determined from an 11C-acetate PET study and vasodilator MBF from a 13N-ammonia study. Results: MBF at rest (0.55 ± 0.10 ml/min/g), after vasodilation (1.20 ± 0.45 ml/min/g), and MVO₂ (0.082 ± 0.014/min) did not change by mid-term CRT at a global level (0.57 ± 0.11 ml/min/g; 1.32 ± 0.49 ml/min/g; 0.085 ± 0.018/min), whereas the rate pressure product (RPP) normalised MVO₂ decreased from 0.104 ± 0.024 to 0.086 ± 0.018/min (p = 0.02). At baseline, the regional analysis revealed significantly higher values for all parameters in the lateral wall than for those in the other walls. Under CRT the regional differences between the resting parameters equalised and all parameters showed significant lower coefficients of variation. Conclusion: Effects of mid-term CRT on resting MBF, vasodilator MBF and MVO₂ occur at a regional level. The resynchronisation is associated with a more homogenous distribution pattern of these parameters among the myocardial walls. Substantial alterations to global MBF at rest, after vasodilation or to MVO₂ are not detectable. Regarding the RPP normalised MVO₂, there is evidence of improved ventricular efficiency through CRT.

Zusammenfassung

Ziel: Bei Patienten mit chronischer Herzinsuffizienz können durch eine kardiale Resynchronisationstherapie (CRT) Hämodynamik und klinische Symptomatik gebessert werden. Die vorliegende Studie untersuchte die Auswirkungen einer 4monatigen CRT auf den myokardialen Blutfluss (MBF) in Ruhe, unter Vasodilatation sowie auf den myokardialen Sauerstoffverbrauch (MVO₂). Patienten, Methoden: Bei 16 Patienten mit idiopathischer dilatativer Kardiomyopathie vor und während biventrikulärer CRT. MBF und MVO₂ im Ruhezustand wurden mittels 11C-Acetat PET und MBF unter Vasodilatation mittels 13N-Ammoniak PET bestimmt. Ergebnisse: Der globale MBF in Ruhe (0,55 ± 0,10 ml/min/g), unter Vasodilatation (1,20 ± 0,45 ml/ min/g) und der MVO₂ (0,082 ± 0,014/min) änderten sich während der CRT nicht (0,57 ± 0,11 ml/min/g; 1,32 ± 0,49 ml/min/g; 0,085 ± 0,018/min). Der auf das Blutdruck-Frequenz-Produkt (RPP) normalisierte MVO₂ sank von 0,104 ± 0,024 auf 0,086 ± 0,018/min (p = 0,02). Die regionale Auswertung ergab für alle Parameter vor der CRT in der Lateralwand signifikant höhere Werte als in den anderen Wänden. Durch die CRT glichen sich bei den Ruhewerten die Unterschiede aus. Alle Parameter wiesen signifikant niedrigere Variationskoeffizienten auf. Schlussfolgerungen: Auf regionaler Ebene zeigen sich Auswirkungen einer CRT auf den MBF in Ruhe und unter Vasodilatation sowie auf den MVO₂ in Form einer geringeren Variabilität der Parameter im Myokard. Grundsätzliche Änderungen des globalen MBF in Ruhe, unter Vasodilatation und des MVO₂ ergeben sich nicht. Betrachtet man den RPP-normalisierten MVO₂, weist dieser auf eine bessere Effizienz des Ventrikels durch die CRT hin.

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