The principle findings of our study are: (1) the diagnostic assessment of most coronary artery segments in patients with PHVs was not hampered by PHV-related artefacts, (2) Björk–Shiley tilting disc PHVs, Sorin tilting disc PHVs and Duromedics bileaflet PHVs precluded complete diagnostic assessment of coronary artery segments; and (3) ON-X and Medtronic Hall PHVs, biological PHVs and annuloplasty rings never hampered coronary artery assessment by MDCT.
The PHV-related artefacts on MDCT images seem to be more dependent on PHV composition than on the PHV design (bileaflet, tilting disc and biological valves) (Table 4) [8, 9]. As far as the material of the PHV is concerned our study showed notable differences.
Björk–Shiley and Sorin tilting disc PHVs as well as Duromedics bileaflet PHVs demonstrated severe artefacts which precluded diagnostic coronary assessment of RCA, LCX and the distal segment of the LAD, dependent on the PHV position. This finding is supported by previous studies that described that these PHV types as being associated with valve-related artefacts that also prohibit the evaluation of the PHV itself on MDCT [8, 9, 11, 12]. The severe artefacts of the Björk–Shiley, Sorin tilting disc and Duromedics bileaflet PHVs were caused by the cobalt-chrome alloy that is present in these valves. Therefore, MDCT is not suitable for the assessment of the coronary arteries in patients who have one of these PHVs implanted. The Saint Jude PHV, consisting of a nickel alloy, produced fewer artefacts but still enough to preclude assessment of a limited number of coronary artery segments in the right coronary artery and circumflex territory (segments 1, 13 and 14). The other segments did not suffer from artefacts that precluded assessment. The Saint Jude PHV is one of the most commonly implanted PHV types worldwide and therefore one of the most likely PHVs to be encountered. The possibility of the non-diagnostic image quality of the above-mentioned segments should be kept in mind when performing cardiac CT in these patients.
In general, Carbomedics, ON-X and Medtronic Hall mechanical PHVs caused no PHV-related artefacts hampering coronary artery assessment. These PHVs are mainly composed of titanium alloys that are associated with only limited artefacts on MDCT .
The biological PHVs and annuloplasty rings produced fewer PHV artefacts than mechanical PHVs on MDCT. Some biological PHVs have a radiopaque frame that supports the valve leaflets, but this does not generally induce many artefacts [2, 9]. In our study, no PHV-related artefacts that interfered with diagnostic coronary assessment were found in biological PHVs or annuloplasty rings.
Prosthetic heart valves in the aortic position may show mainly artefacts in the proximal RCA (segments 1 and 2) because of the close relationship between the aortic PHV and the proximal RCA. Interestingly, the left main branch, which also has a close relationship with the aortic PHV, did not show any PHV-related artefacts. The reason for the absence of PHV-related artefacts in this segment may be the angulation of the PHV with respect to the X-ray beam of the gantry.
In the mitral position, PHV-related artefacts occurred in the LCX and MO branches. The close relationship between these segments and the mitral PHV position is a likely explanation for the presence of the PHV-related artefacts in these specific segments.
Our study contains many different PHV types. A few PHV types are only represented in small numbers. However the most commonly implanted PHVs (Carbomedics, St Jude, Medtronic Hall and the Perimount biological PHVs) are present in considerable numbers. The mean heart rate of 73 ± 18 bpm is relatively high for CT coronary assessment because 79 of 82 CTAs (96%) were performed for other clinical indications without a specific heart rate reduction. High heart rates may cause considerable motion artefacts that influence diagnostic CAD assessment. However, the specific interest of this study was to address the question: do PHV-related artefacts disturb coronary assessment? Other reports emphasised the importance of an optimal heart rate and the restricted diagnostic value of MDCT in the detection of CAD in distal coronary segments . To optimize coronary image quality, beta-blockers and nitroglycerin should be routinely administered in patients without contraindications for these drugs. In this study, CT coronary angiography was not compared with conventional coronary angiography. Further prospective studies are required to determine the diagnostic accuracy of CT coronary angiography in patients after PHV implantation. However, as most commonly implanted PHV types generate only limited artefacts, we would expect the diagnostic accuracy to be close to published results in patients who have not yet undergone PHV implantation . Consensus reading was performed. Interobserver variability has to be investigated in further studies to validate the PHV-related artefacts scoring system. Axial CT images only were assessed for the presence of PHV-related artefacts. Multiplanar reconstructions were not separately assessed because PHV-related artefacts were present in both axial and multiplanar reconstructions.
In conclusion, the most commonly implanted PHVs do not cause artefacts that prohibit coronary artery assessment of at least one coronary segment by MDCT. Carbomedics, Medtronic Hall and ON-X mechanical PHVs, bioprosthesis, and annuloplasty rings virtually never hamper coronary artery assessment by MDCT. However, in patients with a Björk–Shiley or Sorin tilting PHV, coronary artery assessment by MDCT is virtually always hampered by PHV induced artefacts.