In vivo heating of pacemaker leads during magnetic resonance imaging

Aims Magnetic resonance imaging (MRI) is well established as an important diagnostic tool in medicine. However, the presence of a cardiac pacemaker is usually regarded as a contraindication for MRI due to safety reasons. In this study, heating effects at the myocardium-pacemaker lead tip interface have been investigated in a chronic animal model during MRI at 1.5 Tesla. Methods and results Pacemaker leads with additional thermocouple wires as temperature sensors were implanted in nine animals. Temperature increases of up to 20°C were measured during MRI of the heart. Significant impedance and minor stimulation threshold changes could be seen. However, pathology and histology could not clearly demonstrate heat-induced damage. Conclusions MRI may produce considerable heating at the lead tip. Changes of pacing parameters due to MRI could be seen in chronic experiments. Potential risk of tissue damage cannot be excluded even though no reproducible alterations at the histological level could be foun

Heating of pacemaker leads during magnetic resonance imaging: reply

ISSN:1522-9645ISSN:0195-668

Electrical stimulation of primary neonatal rat ventricular cardiomyocytes using pacemakers

The study of gene regulation in cardiac myocytes requires a reliable in vitro model. However, monolayer cultures used for this purpose are typically not exposed to electrical stimulation, though this has been shown to strongly affect cardiomyocyte gene expression. Based on pacemakers for clinical use, we developed an easy-to-use portable system that allows the user to perform electro-stimulation of cardiomyocyte cultures in standard tissue incubators without the need for bulky equipment. In addition, we present a refined protocol for culturing high-purity cardiomyocyte cultures with excellent contractile properties for a wide variety of applications

In vivo heating of pacemaker leads during magnetic resonance imaging

Aims Magnetic resonance imaging (MRI) is well established as an important diagnostic tool in medicine. However, the presence of a cardiac pacemaker is usually regarded as a contraindication for MRI due to safety reasons. In this study, heating effects at the myocardium-pacemaker lead tip interface have been investigated in a chronic animal model during MRI at 1.5 Tesla. Methods and results Pacemaker leads with additional thermocouple wires as temperature sensors were implanted in nine animals. Temperature increases of up to 20°C were measured during MRI of the heart. Significant impedance and minor stimulation threshold changes could be seen. However, pathology and histology could not clearly demonstrate heat-induced damage. Conclusions MRI may produce considerable heating at the lead tip. Changes of pacing parameters due to MRI could be seen in chronic experiments. Potential risk of tissue damage cannot be excluded even though no reproducible alterations at the histological level could be foun

Electrical signals affect the cardiomyocyte transcriptome independently of contraction

Martherus RS, Vanherle SJ, Timmer ED, Zeijlemaker VA, Broers JL, Smeets HJ, Geraedts JP, Ayoubi TA. Electrical signals affect the cardiomyocyte transcriptome independently of contraction. Physiol Genomics 42A: 283-289, 2010. First published September 21, 2010; doi:10.1152/physiolgenomics.00182.2009.-Cardiomyocytes in vivo are continuously subjected to electrical signals that evoke contractions and instigate drastic changes in the cells' morphology and function. Studies on how electrical stimulation affects the cardiac transcriptome have remained limited to a small number of heart-specific genes. Furthermore, these studies have ignored the interplay between the electrical excitation and the subsequent contractions. We carried out a genomewide assessment of the effects of electrical signaling on gene expression, while distinguishing between the effects deriving from the electrical pulses themselves and the effects instigated by the evoked contractions. Changes in gene expression in primary cultures of neonatal ventricular cardiomyocytes from Lewis Rattus norvegicus were investigated with microarrays and RT-quantitative PCR (QPCR). A series of experiments was included in which the culture medium was supplemented with the contraction inhibitor blebbistatin to allow for electrical stimulation in the absence of contraction. Electrical stimulation was shown to directly enhance calcium handling and induce cardiomyocyte differentiation by arresting cell division and activating key cardiac transcription factors as well as additional differentiation mechanisms such as wnt signaling. Several genes involved in metabolism were also directly activated by electrical stimulation. Furthermore, our data suggest that contraction exerts negative feedback on the transcription of various genes. Together, these observations indicate that intercellular electric currents between adjacent cardiomyocytes have an important role in cardiomyocyte development. They act at least partially through a pulse-specific gene expression program that is activated independently from the evoked contractions