Tc-99m hydroxymethylene diphosphonate scintigraphy, computed tomography, and magnetic resonance imaging of osteonecrosis in the mandible: Osteoradionecrosis versus medication-related osteonecrosis of the jaw.

PURPOSE: To present characteristic findings of Tc-99m hydroxymethylene diphosphonate (HMDP) scintigraphy, computed tomography (CT), and magnetic resonance (MR) imaging for osteonecrosis in the mandible, especially osteoradionecrosis (ORN) and medication-related osteonecrosis of the jaw (MRONJ). MATERIALS AND METHODS: Thirteen patients with MRONJ and 7 patients with ORN in the mandible underwent Tc-99m HMDP scintigraphy, CT, and MR imaging (T1-weighted images [T1WI], T2-weighted images [T2WI], short inversion time inversion recovery images [STIR]), diffusion-weighted images [DWI], and apparent diffusion coefficient [ADC] mapping). The associations of scintigraphy, CT, and MR imaging findings with MRONJ and ORN were analyzed using the chi-square test with the Pearson exact test. RESULTS: Thirteen patients with MRONJ and 7 patients with ORN in the mandible showed low signal intensity on T1WI and ADC mapping, high signal intensity on STIR and DWI, and increased uptake on scintigraphy. Periosteal bone proliferation on CT was observed in 69.2% of patients with MRONJ (9 of 13) versus 14.3% of patients with ORN (1 of 7) (P=0.019). CONCLUSION: This study presented characteristic imaging findings of MRONJ and ORN on scintigraphy, CT, and MR imaging. Our results suggest that CT can be effective for detecting MRONJ and ORN.

Shear wave elastography in differentiating between benign and malignant cervical lymph nodes in patients with oral carcinoma.

OBJECTIVES: To evaluate shear wave elastography in differentiating between benign and malignant cervical lymph nodes in patients with oral carcinoma. METHODS: 77 patients with oral squamous cell carcinoma were examined by B-mode and shear wave elastography with a 14 MHz linear transducer. The integrated shear wave elastography software allowed the operator to place regions of interest of various sizes within the elastography window, and automatically displayed shear elastic modulus data (kPa) for each region of interest. The relationship between size and shear elastic modulus of cervical lymph nodes was assessed by Pearson's rank correlation test. The shear elastic modulus of cervical lymph nodes in benign and malignant were evaluated using the Mann-Whitney U test. The analyses were used with a 5% significance level. RESULTS: We plotted shear elastic modulus (X) against minimal axial diameter of cervical lymph nodes (Y), and observed a significant correlation [ Y = 0.091 X + 4.648 (R2 = 0.603, p = 0.000, N = 77)]. Furthermore, the shear elastic modulus of the malignant cervical lymph nodes (105.9 ± 5.2 kPa) was higher than that of benign (11.9 ± 4.4 kPa, p = 0.000). CONCLUSIONS: The shear wave elastography is an effective technique for the objectively and quantitatively diagnosis of cervical lymph node metastases of the oral carcinoma.

Diffusion-weighted Magnetic Resonance Imaging in Odontogenic Keratocysts: Preliminary Study on Usefulness of Apparent Diffusion Coefficient Maps for Characterization of Normal Structures and Lesions.

OBJECTIVE: To investigate the usefulness of diffusion-weighted magnetic resonance imaging (DWI) in odontogenic keratocysts, especially apparent diffusion coefficient (ADC) maps for the characterisation of normal structures and cystic lesions in the jaw. METHODS: Sixteen patients who underwent magnetic resonance imaging (MRI) for the diagnosis of a cystic lesion in the jaw were included in this prospective study. DWI was performed on a 1.5 T unit with b factor of 0 and 800 s/mm2, and ADC maps were generated. ADC values were measured for the normal structures in the upper neck area and for the cystic lesion in the jaw. RESULTS: The mean ADC value of the cerebrospinal fluid (3.66 ± 0.47 × 10-3 mm2/s) in the upper neck area was higher than that of the nasal mucosa (1.80 ± 0.19 × 10-3 mm2/s), Waldeyer's ring (0.75 ± 0.11 × 10-3 mm2/s) and the spinal cord (0.71 ± 0.20 × 10-3 mm2/s). The mean ADC value of the five odontogenic keratocysts (1.03 ± 0.31 × 10-3 mm2/s) was lower than that of the one simple bone cyst (2.79 × 10-3 mm2/s), three nasopalatine duct cysts (2.28 ± 0.12 × 10-3 mm2/s), three radicular cysts (1.82 ± 0.71 × 10-3 mm2/s) and four dentigerous cysts (1.67 ± 1.06 × 10-3 mm2/s). CONCLUSION: This study suggested the usefulness of DWI in odontogenic keratocysts, especially ADC maps for the characterization of normal structures and cystic lesions in the jaw.

Age-related changes in the pulp chamber of maxillary and mandibular molars on cone-beam computed tomography images.

OBJECTIVES: Secondary dentine is laid on pulp chamber walls with increasing age, and decreases pulp chamber size. This study aimed to investigate age estimation on cone-beam computed tomography (CBCT) images for forensic science, and the relationship between age and pulp chamber area of maxillary and mandibular molars. METHODS: We reviewed the CBCT images of 316 first molars in 87 patients with dental lesions. The 87 patients were classified into three groups: younger, 11-28 years; middle-aged, 34-59 years; and older, 60-74 years. The relationship between age and pulp chamber area of maxillary and mandibular molars was evaluated. RESULTS: The mean pulp chamber area of maxillary molars was 8.4 ± 2.0, 4.4 ± 1.7, and 2.9 ± 0.9 mm2 in the younger, middle-aged, and older groups, respectively, (p = 0.028). The mean pulp chamber area of mandibular molars was 10.5 ± 2.3, 6.7 ± 2.2, and 3.7 ± 1.5 mm2 in the younger, middle-aged, and older groups, respectively, (p = 0.000). The mean pulp chamber area of mandibular molars was larger than that of maxillary molars in the younger (p = 0.000), middle-aged (p = 0.000), and older (p = 0.094) groups. The mean pulp chamber area of maxillary and mandibular molars was significantly correlated with age [Y = -0.142X + 11.582 (R 2 = 0.586, p = 0.000) and Y = -0.163X + 14.249 (R 2 = 0.609, p = 0.000), respectively]. CONCLUSIONS: These findings should be useful for diagnosis and treatment planning in dental practice and age estimation in forensic science.

Diffusion-weighted magnetic resonance imaging in oral and maxillofacial lesions: preliminary study on diagnostic ability of apparent diffusion coefficient maps.

OBJECTIVES: The aim of this study was to investigate the usefulness of diffusion-weighted magnetic resonance imaging (DWI) in oral and maxillofacial lesions, especially the utility of apparent diffusion coefficient (ADC) maps for differential diagnosis of these lesions. METHODS: Fifty-seven patients who underwent magnetic resonance imaging for diagnosis of oral and maxillofacial lesions were included in this prospective study. DWI was performed on a 1.5 T unit with b-factors of 0 and 800 s/mm2, and ADC maps were generated. ADC values were measured for all 57 oral and maxillofacial lesions (19 squamous cell carcinoma, 10 medication-related osteonecrosis of the jaw, 6 odontogenic abscess, 4 ranula, 4 osteoradionecrosis, 4 hemangioma, 3 pleomorphic adenoma, 3 odontogenic keratocyst, 2 nasopalatine duct cyst, 1 malignant melanoma, and 1 basal cell carcinoma). RESULTS: The mean ADC values for ranula (2.69 ± 0.59 × 10-3 mm2/s) and nasopalatine duct cyst (2.34 ± 0.12 × 10-3 mm2/s) were significantly higher than those for the other oral and maxillofacial lesions (p = 0.000). In contrast, the mean ADC value for odontogenic abscess (0.67 ± 0.36 × 10-3 mm2/s) was significantly lower than those for the other oral and maxillofacial lesions (p = 0.000). CONCLUSIONS: The present study suggests the usefulness of DWI in oral and maxillofacial lesions, especially the utility of ADC maps for differential diagnosis of these lesions.

Usefulness of shear wave elastography in the diagnosis of oral and maxillofacial diseases.

PURPOSE: To evaluate the usefulness of shear wave elastography in the diagnosis of oral and maxillofacial diseases. MATERIALS AND METHODS: Ten patients with oral and maxillofacial diseases and 28 volunteers drawn from our student doctors were examined by shear wave elastography with a 14-MHz linear transducer using an Aplio 300 apparatus (Canon Medical Systems, Otawara, Japan). A statistical analysis of the shear elastic modulus (kPa) of healthy tissue (the sublingual gland, submandibular gland, anterior belly of the digastric muscle, and geniohyoid muscle) in the 28 volunteers was performed using 1-way repeated measures analysis of variance with the Tukey honest significant difference test. The maximum shear elastic modulus (kPa) of 8 patients with squamous cell carcinoma (SCC) and 2 patients with benign lesions was evaluated with the Mann-Whitney U test. The analysis used a 5% significance level. RESULTS: The mean shear elastic modulus of the sublingual gland (9.4±3.7 kPa) was lower than that of the geniohyoid muscle (19.2±9.2 kPa, P=.000) and the anterior belly of the digastric muscle (15.3±6.1 kPa, P=.004). The maximum shear elastic modulus of the SCCs (109.6±14.4 kPa) was higher than that of the benign lesions (46.4±26.8 kPa, P=.044). CONCLUSION: Our results demonstrated the usefulness of shear wave elastography in the diagnosis of oral and maxillofacial diseases. Shear wave elastography has the potential to be an effective technique for the objective and quantitative diagnosis of oral and maxillofacial diseases.

Magnetic Resonance Sialography and Salivary Gland Scintigraphy of Parotid Glands in Sjögren's Syndrome.

OBJECTIVE: To assess the correlation between conventional magnetic resonance (MR) imaging and MR sialography of parotid glands with salivary gland scintigraphy in patients with Sjögren's syndrome. METHODS: A retrospective study was conducted on eight patients with Sjögren's syndrome who underwent MR imaging and salivary gland scintigraphy. Conventional MR imaging techniques, such as T1-weighted images (T1WI), T2-weighted images (T2WI), and short TI inversion recovery images (STIR) were used for changes of fat signal in the parotid gland, while the MR sialography were used for ducts dilation of the parotid gland. Regarding scintigraphy, time-activity curves of each parotid gland were analysed. The salivary gland excretion fraction was defined as A (before stimulation test (counts/20 s)) and B (after stimulation test (counts/20 s)). RESULTS: Regarding characteristic appearances of fat signal, the A/B of parotid gland with homogeneous intensity distribution (3.51 ± 0.75) was higher than that with heterogeneous intensity distribution (1.56 ± 0.66, P = 0.001). Regarding MR sialographic stages, the A/B of parotid gland with stage 0 (3.51 ± 0.75) was higher than that with stage 1 (2.03 ± 0.86, P = 0.009) and with stage 2 (1.26 ± 0.25, P = 0.000). CONCLUSION: The results suggest that MR sialography of the parotid glands is a useful noninvasive tool for evaluating the decrease of salivary gland excretion in patients with Sjögren's syndrome.

Strain elastography of tongue carcinoma using intraoral ultrasonography: A preliminary study to characterize normal tissues and lesions.

PURPOSE: The aim of this study was to evaluate the quantitative strain elastography of tongue carcinoma using intraoral ultrasonography. MATERIALS AND METHODS: Two patients with squamous cell carcinoma (SCC) who underwent quantitative strain elastography for the diagnosis of tongue lesions using intraoral ultrasonography were included in this prospective study. Strain elastography was performed using a linear 14 MHz transducer (Aplio 300; Canon Medical Systems, Otawara, Japan). Manual light compression and decompression of the tongue by the transducer was performed to achieve optimal and consistent color coding. The variation in tissue strain over time caused by the compression exerted using the probe was displayed as a strain graph. The integrated strain elastography software allowed the operator to place circular regions of interest (ROIs) of various diameters within the elastography window, and automatically displayed quantitative strain (%) for each ROI. Quantitative indices of the strain (%) were measured for normal tissues and lesions in the tongue. RESULTS: The average strain of normal tissue and tongue SCC in a 50-year-old man was 1.468% and 0.000%, respectively. The average strain of normal tissue and tongue SCC in a 59-year-old man was 1.007% and 0.000%, respectively. CONCLUSION: We investigated the quantitative strain elastography of tongue carcinoma using intraoral ultrasonography. Strain elastography using intraoral ultrasonography is a promising technique for characterizing and differentiating normal tissues and SCC in the tongue.

Comparison between squamous cell carcinoma and inflammatory diseases of the oral and maxillofacial region using gallium-67 scintigraphy with computed tomography and magnetic resonance imaging.

PURPOSE: This study aimed to compare squamous cell carcinoma (SCC) with inflammatory diseases of the oral and maxillofacial region using gallium 67 (67Ga) scintigraphy with computed tomography (CT) and magnetic resonance imaging (MRI). MATERIAL AND METHODS: Seventy patients with SCC and 15 patients with inflammatory diseases of the oral and maxillofacial region underwent 67Ga scintigraphy with CT and MRI. A comparison between imaging features of 67Ga scintigraphy, CT, and MRI and lesions was performed with the Pearson's chi-squared test. RESULTS: 67Ga scintigraphy was positive for 25 of 39 patients with SCC positive on CT and/or MRI (64.1%) and for 13 of 15 patients with inflammatory diseases positive on CT and/or MRI (86.7%). The detection of inflammatory diseases with 67Ga scintigraphy was higher than that of SCC (p = 0.104). CONCLUSIONS: This study compared SCC with inflammatory diseases of the oral and maxillofacial region using 67Ga scintigraphy with CT and MRI. 67Ga scintigraphy is an effective technique for detection of inflammatory diseases of the oral and maxillofacial region.

Submandibular sialolithiasis with CT and scintigraphy: CT values and salivary gland excretion in the submandibular glands.

PURPOSE: Sialolithiasis is one of the most prevalent large obstructive disorders of the submandibular glands. The aim of this study was to investigate submandibular sialolithiasis with computed tomography (CT) and scintigraphy, with a particular focus on the relationship between CT values of the submandibular glands and their excretion rate. MATERIALS AND METHODS: Fifteen patients with submandibular sialolithiasis who underwent CT and salivary gland scintigraphy were included in this study. The relationship between the CT values of submandibular glands with and without sialoliths and salivary gland excretion measured using salivary gland scintigraphy was statistically analyzed. Dynamic images were recorded on the computer at 1 frame per 20 seconds. The salivary gland excretion fraction was defined as A (before stimulation test [counts/frame]) / B(after stimulation test [counts/frame]) using time-activity curves. RESULTS: The CT values in the submandibular glands with and without sialoliths was 9.9±44.9 Hounsfield units (HU) and 34.2±21.8 HU, respectively (P=.233). Regarding the salivary gland excretion fraction using scintigraphy, the A/B value in the submandibular glands with sialoliths (1.09±0.23) was significantly lower than in the submandibular glands without sialoliths (1.99±0.57, P=.000). CONCLUSION: Assessments of the CT values and the salivary gland excretion fraction using scintigraphy in the submandibular glands seem to be useful tools evaluating submandibular sialolithiasis.

Gallium-67 Scintigraphy in Differential Diagnosis of Malignant Tumours from Non-Tumorous Lesions of the Maxilla.

OBJECTIVE: To assess the gallium-67 (67Ga) scintigraphy in differential diagnosis of malignant tumours from non-tumorous lesions of the maxilla. METHODS: Nineteen patients with malignant tumours (six cases of squamous cell carcinoma and one case of malignant melanoma) and non-tumorous lesions (seven cases of maxillary sinusitis and five cases of postoperative maxillary changes) in the maxilla underwent 67Ga and bone scintigraphy with CT and MRI. The statistical analysis with respect to comparison between imaging features of 67Ga and bone scintigraphy and maxillary lesions was performed with the Pearson's chi-squared test. RESULTS: 67Ga scintigraphy for six of the seven patients with malignant tumours in the maxilla was positive (85.7%), 0 of 12 patients with non-tumorous lesions were positive (0%) (P = 0.000). Bone scintigraphy for six out of seven patients with malignant tumours was positive (85.7%), 10 of 12 patients with non-tumorous lesions were positive (83.3%) (P = 0.891). CONCLUSION: 67Ga scintigraphy was useful for detection of malignant tumours in the maxilla. However, bone scintigraphy was not an effective technique for interpretation of malignant tumours, maxillary sinusitis and postoperative change in the maxilla.

Osteosarcoma of the Mandible: a Case Report with CT, MRI and Scintigraphy.

Osteosarcomas are especially rare in the mandible and maxilla, representing 1.6% of all bony malignant tumours. In this article, we described a case of osteosarcoma of the mandible. Computed tomography (CT) image showed a well-circumscribed homogeneous mass, with nonhomogeneous contrast enhancement. T1-weighted magnetic resonance imaging (MR) image showed intermediate signal intensity on, and after administration the lesion showed signal intensity lower than muscle. T2-weighted MR image showed heterogeneous high signal intensity. Bone scintigraphy revealed monostatic involvement of the mandible with a homogenous intense uptake pattern. Ga-67 citrate scintigraphy revealed significantly increased uptake. Histopathological examination confirmed the diagnosis of osteosarcoma.

A Rare Case of Malignant Melanoma of the Mandible: CT and MRI Findings.

Malignant melanoma of the mandibular gingiva is extremely rare. It is a malignant tumour of melanocytes or their precursor cells, and often misinterpreted as a benign pigmented process. A few reports have described computed tomography (CT) and magnetic resonance imaging (MRI) findings of malignant melanoma in the oral cavity. We report a rare case of malignant melanoma of the mandible and the related CT and MRI findings. Soft tissue algorithm contrast-enhanced CT showed an expansile mass and irregular destruction of alveolar bone in the right side of the mandibular molar area. MR images showed an enhancing mass and the tumour had a low to intermediate signal intensity and a high-signal intensity. Soft tissue algorithm contrast-enhanced CT and MR images showed lymphadenopathy involving the submandibular lymph nodes. Histopathological examination confirmed the diagnosis of malignant melanoma.

Structural Variations in Parotid Glands Induced by Radiation Therapy in Patients with Oral Carcinoma Observed on Contrast-Enhanced Computed Tomography.

BACKGROUND: Xerostomia is one of the commonest radiation-induced complications in patients with head and neck carcinoma. The aim of this study was to assess structural variations in parotid glands induced by radiation therapy in patients with oral carcinoma with contras-enhanced computed tomography (CECT). MATERIAL/METHODS: A retrospective study was performed in 41 patients with oral carcinoma who underwent CECT for head and neck malignancies before and after radiotherapy. We analyzed the relationship between parotid density variations, parotid volume change, as seen on CECT, and the mean radiation dose applied to the parotid glands in patients with oral carcinoma immediately after radiotherapy, and 2 and 3 years later. RESULTS: Immediately after radiotherapy, high-density changes on contrast-enhanced CT were observed in 70.5% of the irradiated parotids. Low-density changes due to fat degeneration were seen in 46.2% and 72.2% of the irradiated parotids 2 and 3 years after radiotherapy, respectively. The mean dose applied to the parotids with the low-density changes and without such changes 3 years after radiotherapy was 46.0 Gy and 27.7 Gy, respectively (p=0.049). Furthermore, parotid shrinkage was observed in 63.6% of the irradiated parotids. CONCLUSIONS: This study suggests that the structural variations in parotid glands induced by radiotherapy included high-density changes that were observed immediately after radiotherapy and low-density changes that were seen at late follow-up. This study should be useful for clinicians in the assessment of radiation-induced injuries in the parotids with respect to early prediction of xerostomia.

Characteristic Multimodal Imaging of Medication-Related Osteonecrosis of the Jaw: Comparison Between Oral and Parenteral Routes of Medication Administration.

BACKGROUND: To assess multimodal imaging features of medication-related osteonecrosis of the jaw (MRONJ) and to analyze the differences between oral and parenteral routes of medication administration. We retrospectively reviewed panoramic radiographs, CT, MRI, and bone scintigraphy of patients with MRONJ. MATERIAL/METHODS: A retrospective study was conducted in 16 patients with MRONJ who underwent panoramic radiography, CT, MRI, and bone scintigraphy. Statistical analysis for the comparison between routes of medication administration and multimodal imaging features was performed with the Pearson's χ2 test. RESULTS: The percentage of cases with sequestrum separation was 25.0% (4/16 cases) on panoramic radiography and 81.3% (13/16 cases) on CT. The percentage of cases with periosteal bone proliferation on CT was 41.7% (5/12 cases) in the oral route of administration vs. 100% (4/4 cases) in the parenteral route of administration (p=0.042). The percentage of cases with spread of soft tissue inflammation to buccal and other spaces on CT and MRI was 33.3% (4/12 cases) in the oral route of administration vs. 100% (4/4 cases) in the parenteral route of administration (p=0.021). CONCLUSIONS: The sequestrum separation on panoramic radiography in patients with MRONJ was unclear in comparison to CT. Furthermore, characteristic CT findings of patients with MRONJ in the parenteral administration group were periosteal bone proliferation and spread of soft tissue inflammation to buccal and other spaces.

Diffusion-Weighted Imaging in the Oral and Maxillofacial Region: Usefulness of Apparent Diffusion Coefficient Maps and Maximum Intensity Projection for Characterization of Normal Structures and Lesions.

BACKGROUND: The aim of this study was to investigate diffusion-weighted imaging (DWI) in the oral and maxillofacial region, with a special focus on the usefulness of apparent diffusion coefficient (ADC) maps and maximum intensity projection (MIP) for characterization of normal structures and lesions. MATERIAL/METHODS: Thirty-five patients who underwent magnetic resonance imaging (MRI) for diagnosis of oral and maxillofacial lesions were included in this prospective study. DWI was performed on a 1.5 T unit, with b factor of 0 and 800 s/mm2; moreover, ADC maps were generated. ADC values were measured for normal structures, odontogenic infections, squamous cell carcinomas (SCC), and hemangiomas. RESULTS: As regards the normal structures, the mean ADC value of the cerebrospinal fluid (3.65±0.60×10-3 mm2/s) in the upper neck area was higher than that of the spinal cord (0.74±0.15×10-3 mm2/s, P=0.000), lymph nodes (0.87±0.17×10-3 mm2/s, P=0.000), and Waldeyer's ring (0.92±0.29×10-3 mm2/s, P=0.000). The mean ADC value of hemangiomas (1.52±0.31×10-3 mm2/s) was higher than that of odontogenic infections (0.85±0.36×10-3 mm2/s, P=0.034) and SCC (1.38±0.22×10-3 mm2/s, P=0.840). Furthermore, MIP (DWI) showed the normal structures and lesions in the oral and maxillofacial region in an improved way. CONCLUSIONS: DWI, ADC maps, and MIP can be used to characterize and differentiate normal structures and lesions in the oral and maxillofacial region.

Apparent disappearance of ventricular parasystole due to a marked difference between the long form and the short form of the ectopic cycles.

Electrocardiograms were taken from a 44-year-old man with irregular ventricular parasystole in whom pure parasystolic cycles without any intervening nonectopic QRS complexes were found. When a sinus impulse fell late in the parasystolic cycle, it hastened occurrence of the next parasystolic discharge. This suggested that type I second degree entrance block occurred in the re-entrant pathway containing the parasystolic focus. When a sinus impulse fell early in the parasystolic cycle, it delayed occurrence of the next parasystolic discharge. This suggested that electrotonic modulation occurred in the parasystolic focus. As a result, the difference in length between the short form and the long form of the parasystolic cycle became markedly great. When the length of two adjacent sinus cycles ranged between the short and the long parasystolic cycle, manifest parasystolic QRS complexes disappeared for a long time. In true ventricular parasystole with pure ectopic cycles, such long disappearance has never been reported before.

Magnetic resonance imaging findings of nodular fasciitis in the mental region.

Nodular fasciitis (NF) is a benign reactive lesion of the soft tissues related to the fascia and characterized by fibroblastic proliferation. The most common site is the upper extremities (46%), followed by the head and neck region (20%). In the orofacial region, the lesion typically develops within the subcutaneous structures overlying the angle and inferior border of the mandible and the zygoma. Magnetic resonance imaging (MRI) findings of NF in the orofacial region are almost unreported in the literature. In the present case report, we describe MRI findings of mental NF in a 19-year-old woman. MRI revealed a well-defined, round soft-tissue mass lying on the mentum. On T1-weighted MRI, the lesion was isointense to skeletal muscle; it was hyperintense to skeletal muscle on T2-weighted MRI, and was enhanced by Gd-diethylenetriamine pentaacetic acid (DTPA). Histologic examination revealed abundant myxoid degeneration dispersed in the lesion. The T2-weighted higher heterogeneous signal intensity was likely due to abundant myxoid degeneration or the cellular component of the lesion. A strong bright signal intensity belt appeared in the periphery of the lesion on Gd-DTPA enhancement. This rim enhancement appeared to represent small arterioles and venules that were visible in the peripheral area on histologic examination.

Atrial escape-capture bigeminy in dominant atrial rhythm with 2:1 exit block.

A 27-year-old woman with atrial bigeminy is reported in whom long PP intervals alternate with short PP intervals. All P waves are negative in lead II and all PR intervals measure 0.12 s. In the 12-lead electrocardiogram, however, these P waves were definitely different in configuration from each other, and were divided into two groups. Namely, these negative P waves are divided into those of dominant atrial rhythm J1 with 2:1 exit block, and those of atrial escape J2. Long J1-J2 intervals alternate with short J2-J1 intervals. These electrocardiographic findings show the presence of atrial escape-capture bigeminy. Such atrial escape-capture bigeminy in dominant atrial rhythm with 2:1 exit block has never been reported before.

Apparent bradycardia-dependent right bundle branch block associated with atypical atrioventricular Wenckebach periodicity as a possible mechanism.

The Holter monitor electrocardiogram was taken from a 15-year-old male athlete. Intermittent right bundle branch block frequently occurred at rest. When sinus cycles gradually lengthened, sinus impulses were conducted to the ventricles with right bundle branch block (RBBB) in succession. When, thereafter, sinus cycles gradually shortened, sinus impulses were conducted without RBBB. However, it seems that these findings do not show true bradycardia-dependent RBBB. Atypical atrioventricular Wenckebach periodicity was occasionally found in which sudden shift from the period of comparatively short PR intervals to the period of long PR intervals occurred. In the Wenckebach periodicity, when a QRS complex occurs after a much longer pause, RBBB was not found, while when it occurs after a much shorter period, RBBB was found. This suggests that this case may be apparent bradycardia-dependent RBBB, namely, a form of tachycardia-dependent RBBB. This is the first report suggesting apparent bradycardia-dependent bundle branch block associated with gradual lengthening of sinus cycles, as a possible mechanism.