Optimal patient selection for maze procedure in patients undergoing mitral valve disease.

OBJECTIVES: Although risk factors for unsuccessful Maze procedure have been demonstrated, an appropriate patient selection is still controversial. In our institute, Maze procedure is indicated for those whom normal sinus rhythm (NSR) was reestablished by intraoperative direct cardioversion (DC) after ventricular unloading by total cardiopulmonary bypass. The purpose of this study was to evaluate the effectiveness of our indication criteria for Maze procedure in patients with mitral valve disease. METHODS: Between October 2012 and October 2021, MAZE was indicated in 55 patients in whom normal sinus rhythm (NSR) was reestablished by intraoperative direct current cardioversion (DC). Three endpoints and predictors were examined: disappearance of atrial fibrillation (AF), NSR, and A-wave detection. RESULTS: Restoration of NSR by intraoperative DC was confirmed in 43 patients, and these patients underwent MAZE. AF disappeared in 39 patients (90.7%), and F-wave ≥ 0.1 mV was a significant predictive factor (odds ratio (OR) 20.99, 95% CI 1.22-1079.06). NSR was reestablished in 36 patients (83.7%), and F-wave ≥ 0.1 mV (odds ratio 15.62, 95% CI 1.62-359.86) + AF history ≤ 3 years (OR 8.30, 95% CI 1.09-177.04) were significant predictors. A-wave detection was confirmed in 26 patients (60.5%), and left atrial diameter ≤ 55 mm was a significant predictor (OR 5.22, 95% CI 1.28-24.79). CONCLUSIONS: Intraoperative DC after ventricular unloading resulted effective patient selection for concomitant Maze procedure. F-wave and AF history were predictive factor of electrical restoration of AF, and left atrial diameter was predictive factor of restoration of atrial function.

Clinical impact of the right ventricular impairment in patients following transcatheter aortic valve replacement.

The right ventricular (RV) impairment can predict clinical adverse events in patients following transcatheter aortic valve replacement (TAVR) for severe aortic stenosis (AS). Limited reports have compared impact of the left ventricular (LV) and RV disorders. This retrospective study evaluated two-year major adverse cardiac and cerebrovascular events (MACCE) in patients following TAVR for severe AS. RV sphericity index was calculated as the ratio between RV mid-ventricular and longitudinal diameters during the end-diastolic phase. Of 239 patients, 2-year MACCE were observed in 34 (14%). LV ejection fraction was 58 ± 11%. Tricuspid annular plane systolic excursion (TAPSE) and RV sphericity index were 20 ± 3 mm and 0.36 (0.31-0.39). Although the univariate Cox regression analysis demonstrated that both LV and RV parameters predicted the outcomes, LV parameters no longer predicted them after adjustment. Lower TAPSE (adjusted hazard ratio per 1 mm, 0.84; 95% confidence interval, 0.75-0.93) and higher RV sphericity index (adjusted hazard ratio per 0.1, 1.94; 95% confidence interval, 1.17-3.22) were adverse clinical predictors. In conclusion, the RV structural and functional disorders predict two-year MACCE, whereas the LV parameters do not. Impact of LV impairment can be attenuated after development of RV disorders.

Potential confounders of the obesity paradox in older patients following transcatheter aortic valve replacement.

PURPOSE: A higher body mass index (BMI) is associated with lower mortality in older patients following transcatheter aortic valve replacement (TAVR) for severe aortic valve stenosis. The current study aimed to investigate potential confounders of association between BMI and prognosis. METHODS: The retrospective single-center study included consecutive patients following TAVR and excluded those in whom subcutaneous fat accumulation (SFA), visceral fat accumulation (VFA), and major psoas muscle (MPM) volume were not assessed by computed tomography. Cachexia was defined as a combination of BMI < 20 kg/m2 and any biochemical abnormalities. RESULTS: After 2 patients were excluded, 234 (age, 86 ± 5 years; male, 77 [33%]; BMI, 22.4 ± 3.8 kg/m2; SFA, 109 (54-156) cm2; VFA, 71 (35-115) cm2; MPM, 202 (161-267) cm3; cachexia, 49 [21%]) were evaluated. SFA and VFA were strongly correlated with BMI (ρ = 0.734 and ρ = 0.712, respectively), whereas MPM was weakly correlated (ρ = 0.346). Two-year all-cause mortality was observed in 31 patients (13%). Higher BMI was associated with lower mortality (adjusted hazard ratio [aHR], 0.86; 95% confidence interval [CI], 0.77-0.95). A similar result was observed in the multivariate model including SFA (aHR in an increase of 20 cm2, 0.87; 95% CI, 0.77-0.98) instead of BMI, whereas VFA was not significant. Cachexia was a worse predictor (aHR, 2.51; 95% CI 1.11-5.65). CONCLUSIONS: Association of higher BMI with lower mortality may be confounded by SFA in older patients following TAVR. Cachexia might reflect higher mortality in patients with lower BMI.

Operative Timing and Feasibility of Mitral Valve Repair in Active Infective Endocarditis.

PURPOSE: We studied the association between operative timing and the feasibility of mitral valve (MV) repair in active infective endocarditis (IE). METHODS: Forty-nine active IE patients who underwent MV operation were classified according to operative timing: within 48 hours (Term I: n = 7), between 3 and 14 days (Term II: n = 22), and ≥15 days (Term III: n = 20). Patient profiles, operative outcomes, and feasibility of MV repair were evaluated. Complexity score and severity score were used to define the feasibility of MV repair depending on the extent of infected lesion and technical difficulties. RESULTS: There were no differences in basic profile in the three groups. Rate of major complications was higher in Term I (86%) than II (41%, p = 0.031) and III (25%, p = 0.005). In-hospital mortality was also higher in Term I (43%) than II (9%, p = 0.039) and III (5%, p = 0.015). The three groups did not differ by feasibility of MV repair calculated by the two-score system or by frequency of MV repair (I: 57%, II: 59%, and III: 55%). CONCLUSIONS: Morbidity and mortality were high in urgent cases. Feasibility of MV repair is associated with the extent of infected lesion and technical difficulties, and not with operative timing.

Factors Influencing on the Aneurysm Sac Shrinkage after Endovascular Abdominal Aortic Aneurysm Repair by the Analysis of the Patients with the Aneurysm Sac Shrinkage and Expansion.

Objectives: The aneurysmal sac shrinkage has been reported as the strong predictor of favorable long-term outcome after endovascular aneurysm repair (EVAR). We evaluated the effects of perioperative and intraoperative factors on the aneurysm sac shrinkage. Methods: EVAR was performed for 296 patients during August 2009-December 2021. Nine patients with type Ia, Ib, or III; 69 patients with the sac diameter change less than 5 mm; and five patients with sac re-expansion after shrunk more than 5 mm were excluded. Thus, patients with sac shrinkage 5 mm or more (79 patients, shrinkage group) and with sac expansion 5 mm or more (18 patients) were included in this study. Antifibrinolytic therapy with tranexamic acid (TXA) 1500 mg/day for 6 months after EVAR was introduced in March 2013 and patent aortic side branches were coil embolized during EVAR since July 2015. Patients' background and patent aortic side branches at the end of EVAR were evaluated. Results: Univariate analysis for comparison between patients with sac shrinkage and sac expansion revealed that males (82.3% vs. 55.6%, p = 0.021), without antiplatelet therapy (40.5% vs. 66.7%, p = 0.044) and TXA (79.8% vs. 38.9%, p <0.001), were significantly associated with sac shrinkage. By multivariate analysis, the odds ratio of sac shrinkage was 11.7 for males, 0.1 for the patients on antiplatelet therapy, and 6.5 for the patient who received TXA. The patients with patent inferior mesenteric artery (IMA) were less in the shrinkage group (20.3% vs. 77.8%, p <0.001) and with two or less patent lumbar arteries (LAs) were more in the shrinkage group (82.3% vs. 33.3%, p < 0.001). The odd ratio of sac shrinkage was 7.8 for occluded IMA and 3.9 for two or less patent LAs. Conclusion: The possibility of sac shrinkage would be high for the patient with occluded IMA and two or less patent LA at the end of EVAR, and that patient received TXA after EVAR. (This is a translation of Jpn J Vasc Surg 2022; 31: 291-297.).

Procedure and Aortic Remodeling Effects of Entry Closure with Stentgraft for Type B Aortic Dissection: Comparison between the Patients with Narrow True Lumen and Those with Aneurysmal Dilated False Lumen.

Objectives: Appropriateness of device selection, procedure protocol and aortic remodeling effects of entry closure (TEVAR) with stent-graft (SG) for patent false lumen type B aortic dissection (TBAD) were compared between the patients with narrow true lumen (narrow group) and those with aneurysmal dilated false lumen (aneurysmal group). Methods: Twenty-six patients with narrow true lumen (narrow group) and 20 patients with aneurysmal false lumen (aneurysmal group) were included in this study. In narrow group, straight SG was implanted from Zone 3 regardless the distance between the left subclavian artery and entry. In aneurysmal group, straight or taped SG was implanted with proximal landing zone length 20 mm or more. Thoracic aortic anatomy was evaluated by CT and aortic remodeling was defined as true lumen diameter ≥50% of the aortic diameter and occlusion of false lumen. Aorta related death, retrograde type A aortic dissection (RTAD), stentgraft induced new entry (SINE) and aortic maximum diameter enlargement 5 mm or more (aortic expansion) were included in the aortic event. Results: There was no procedure related complication in narrow group and 1 patient died due to aortic rupture in aneurysmal group, Type Ia endoleak by enhanced CT 7 days after TEVAR was detected in one patient in each group. Achievement of aortic remodeling was significantly better in narrow group. Aortic event occurred in only one patient in narrow group, in whom aortic expansion was observed. In aneurysmal group, aortic event occurred 12 patients (60%) and 2 RTAD, 5 SINE, and 8 aorta expansion were observed. Aortic event free rate was significantly better in narrow group. Conclusion: TEVAR procedure for the TBAD patients with narrow true lumen seemed to be appropriate, however, different TEVAR procedure or additional procedures would be required for those with aneurysmal dilated false lumen to obtain favorable outcomes. (This is secondary publication from Jpn J Vasc Surg 2021; 30: 347-357.).

Midterm Outcomes of Endovascular Abdominal Aortic Aneurysm Repair with Prevention of type 2 Endoleak by Intraoperative Aortic Side Branch Coil Embolization.

OBJECTIVE: The midterm results of endovascular abdominal aortic aneurysm repair (EVAR) with aortic side branch coil embolization during EVAR was evaluated. METHODS: Our center began coil embolization for all patent inferior mesenteric artery (IMA) and lumbar artery (LA) with an inner diameter more than 2.0 mm during EVAR since June 2015. When four or more LA were patent, coil embolization for LA with inner diameter 2.0 mm or less was done. EVAR without aortic side branches coil embolization was performed for 59 patients prior to June 2015 (control group) and 79 patients underwent EVAR with coil embolization during EVAR (coil group). The success rate of coil embolization for IMA and LA was evaluated in coil group. The frequency of type 2 endoleak (T2EL), freedom from aneurysm sac expansion (5 mm or more) rate and the rate of the aneurysm sac shrinkage (10 mm or more) were compared between the coil and control groups. Additionally, multiple logistic regression analysis for all patients was conducted to analyze whether IMA patency and the number of patent lumbar artery at the end of EVAR were the risk factors of the aneurysm sac expansion of 5 mm or more. RESULTS: The success rate of IMA coil embolization was 96.4% and that of LA was 74.5%. Compared to the control group, the frequency of T2EL was significantly lower in coil group at 7 days (1.3% vs. 60.4%, P <0.0001) and at 6 months (2.1% vs 38.2%, P <0.0001) after EVAR. The freedom from aneurysm sac expansion rate was significantly better in the coil group at 5 years (100% in coil group and 65.2% in control group, P = 0.002). The rate of aneurysm sac shrinkage was significantly better in coil group (15.5% vs. 2.0% at 1 year, 42.8% vs. 6.3% at 2 years and 53.4% vs. 17.8% at 3 years, p = 0.0007). The risk of aneurysm sac expansion of 5 mm or more was estimated to be 11 times greater when the IMA was patent, and 4.9 times greater when 3 or more LAs were patent at the end of EVAR. CONCLUSION: When IMA was occluded and the number of patent LA became 2 or less by aortic side branch coil embolization during EVAR, favorable mid-term results were safely obtained and good long-term result could be expected with EVAR.

Influence of transcatheter aortic valve replacement on patients with severe aortic stenosis undergoing non-cardiac surgery.

OBJECTIVES: The purpose of this study was to clarify the influence of transcatheter aortic valve replacement (TAVR) in patients with aortic stenosis (AS) undergoing non-cardiac surgery. METHODS: Thirty-four patients with severe AS diagnosed by preoperative evaluation for non-cardiac surgery were reviewed and compared in two categories. First, patient profiles and surgical risk were compared before (pre-TAVR group; n = 10) and after (post-TAVR group; n = 24) the introduction of TAVR. Second, the completion rate of non-cardiac surgery and interval between the two cardiac and non-cardiac operations were compared between surgical aortic valve replacement (AVR) patients before the introduction of TAVR (pre-AVR group (n = 10)), in AVR patients after the introduction of TAVR (post-AVR (n = 12)), and in TAVR patients (TAVR group (n = 12)). RESULTS: Age and Japan score were higher in the post-TAVR group than in the pre-TAVR group. Malignancy was the most common non-cardiac disease (80%) in the pre-TAVR group, whereas orthopedic disease was the most common (50%) in the post-TAVR group. Completion rate of non-cardiac operation in the pre-AVR, post-AVR and TAVR groups was 70, 33, and 75% (post-AVR vs. TAVR: p = 0.010), and the interval between the two operations was 129 ± 98 days, 87 ± 40 days and 27 ± 15 days, respectively (pre AVR vs. TAVR: p = 0.034 and post AVR vs. TAVR: p = 0.025). In the post-TAVR group, AVR was selected because of a lack of fitness for TAVR in 5 of 12 patients. CONCLUSIONS: After the introduction of TAVR, more senile and high-risk patients became candidates for a two-stage operation, and orthopedic conditions became the most common non-cardiac disease. Innovation in transcatheter valvular interventions and expansion of indications for patients currently evaluated as "unfit for TAVR" might be crucial issues for non-cardiac surgery with severe AS.

[Mitral Valve Plasty in Active Infective Endocarditis].

According to the current guideline, early surgery is recommended in patients with infective endocarditis (IE). On the other hand, mitral valve plasty (MVP) became the preferred surgical option in patients with IE, because of its benefits in the preservation of left ventricular function and prevention of recurrence of infection. Feasibility of MVP is an important issue in surgical strategy, however, it might be associated with the timing of the operation:feasibility of MVP might be higher in healed IE than active IE, although there had been no clear evidence in previous studies. In order to develop scoring system to predict feasibility of MVP in patients with active IE, we have introduced "severity score".Severity score defined as the sum of valvular score which evaluates the extensiveness of the valvular destruction, and technical score which evaluates the complexity and durability of the repair. Probability of feasible MVP was high in severity score≤7 points and low in severity score≥9 points. MVP is basically selected in patients with severity score of 8 points, taking the benefit of patients and risks of longterm durability into consideration. We believe that severity score is valuable and reproducible scoring system in surgical decision making.

Predictive Factor of the Possibility for Aortic Side Branches Coil Embolization during Endovascular Abdominal Aortic Aneurysm Repair.

Objective: Coil embolization of aortic side branches has been additionally performed to prevent type II endoleak during EVAR in our institute. In this study, we evaluated the predictive factors of the possibility for coil embolization of the inferior mesenteric artery (IMA) and lumbar artery (LA) during EVAR. Methods: Seventy-four EVAR patients during June 2015 and April 2019 were included in the study. The coil embolization procedural time for one vessel is limited to 10 min. Aortic side branches were selected with 4 Fr Shepherd hook type catheter (Medikit, Tokyo, Japan) and were embolized with Interlock (Boston Scientific, MA, USA) via microcatheter. As predictive factors, internal diameter of aortic side branches and the aortic diameter perpendicular to the origin of LA (aortic diameter) were evaluated. Results: Coil embolization was tried for 52 patent IMAs and all IMAs except two IMAs with ostial stenosis were successfully coil embolized (96.2%). Totally 190 LAs were patent and coil embolization was tried for 144 LAs. Among 144 LAs, 106 LAs (73.6%) were successfully coil embolized and the diameter was significantly longer (2.30±0.51 mm vs. 2.04±0.41 mm, p=0.007) and aortic dimeter was significantly shorter (30.0±8.1 mm vs. 40.5±11.6 mm, p<0.001) in successfully embolized LAs. Cut off value of successful LA coil embolization was 2.06 mm for internal diameter and 36.1 mm for aortic diameter by receiver operating characteristic curve analysis. Successful coil embolization rate for LAs with internal diameter longer than 2.0 mm and aortic diameter less than 36.2 mm was 90% (72 among 80 LAs). Conclusion: Coil embolization during EVAR for IMA was highly successful, if there was no calcified ostial stenosis. LA embolization was feasible especially for LAs with internal diameter ≥2.0 mm and aortic diameter ≤36.1 mm. This information would be useful to select the target vessel for aortic side branches coil embolization during EVAR. (This is a translation of Jpn J Vasc Surg 2019; 28: 389-396.).

Evaluation and Coil Embolization of the Aortic Side Branches for Prevention of Type II Endoleak after Endovascular Repair of Abdominal Aortic Aneurysm.

Objectives: Aneurysm shrinkage after EVAR is the strong factor of favorable outcomes after endovascular abdominal aortic aneurysm repair (EVAR), and type II endoleaks is the risk factor of no aneurysm shrinkage or aneurysm enlargement in the long term. In this study, we evaluate the aortic side branches relate to early postoperative type II endoleak, and performed coil embolization for those vessels for prevention of type II endoleak. Methods: Patency and diameter of aortic side branches including inferior mesenteric artery (IMA) and lumbar artery (LA) were evaluated in 56 consecutive patients with abdominal aortic aneurysm who were scheduled for EVAR. Coil embolization with Interlock was performed in 24 patients during EVAR for all patent IMA and LA with maximal diameter more than 2.0 mm. Computed tomography was performed one week after EVAR for evaluation of endoleak. Results: In patients with IMA more than 2.5 mm in diameter, the frequency of type II endoleak was approximately 90% regardless of the number of patent LA. In case with patent IMA less than 2.5 mm or with 2 or more patent LA larger than 2.0 mm, the frequency of type II endoleak was 46 to 67%. Coil embolization for IMA was successfully performed in 15/16 patients (94%). Coil embolization of LA was performed for patent LA larger than 2.0 mm and 29 out of 45 LA (64%) were successfully occluded. There was no perioperative complication associated with coil embolization. The frequency of type II endoleak was significantly lower in patients with coil embolization than those without coil embolization (4.2% vs 58.9%, p<0.0001). Conclusion: Patent IMA and LA in diameter larger than 2.0 mm were associated with type II endoleak one week after EVAR, and coil embolization with Interlock during EVAR is safe and effective procedure to prevent type II endoleak. (This is a translation of Jpn J Vasc Surg 2016; 25: 321-328.).

Surgical Outcome in Hemodialysis Patients with Active-Phase Infective Endocarditis.

PURPOSE: The aim of this study was to elucidate the characteristics of chronic hemodialysis (HD) patients requiring surgery during the active phase of infective endocarditis (IE). METHODS: From December 2004 to July 2015, 58 patients underwent surgery in our institute for active IE. Seven patients had been on HD for 1-15 years. Their preoperative profiles and surgical outcomes were compared to those of the other 51 patients (non-HD group). RESULTS: The predominant causative microorganisms in the HD group were Staphylococcus spp, particularly methicillin-resistant Staphylococcus aureus (MRSA), whereas Streptococcus spp were predominant in the non-HD group. Prosthetic dysfunction (stuck valve after mechanical and structural valve dysfunction following bioprosthetic valve replacement), complete atrioventricular (AV) block, and annular abscess formation were more frequent in the HD group. In-hospital mortality was higher in the HD group (29% vs. 6%, p = 0.044). Actuarial survival in the HD and non-HD groups was 43% vs. 87% at 5 years and 43% vs. 76% at 10 years (p = 0.007). CONCLUSIONS: Early and long term outcomes in patients with chronic HD were poor. Compared to other patients, chronic HD patients undergoing valve surgery during active IE had higher incidences of MRSA infection, annular abscess formation, postoperative valve dysfunction, and postoperative complete AV block.

Left atrial thrombus in a patient without mitral valve disease or atrial fibrillation.

A 54-year-old man presented with back pain. His medical history included hypertension and gout. There was no history of heart disease or arrhythmia. The electrocardiogram showed normal sinus rhythm. Chest computed tomography demonstrated a large calcified tumor (65 mm) in the left atrium (LA). The echocardiogram showed a round hyperechoic mass in the enlarged LA (56 mm) attached to the atrial septum without mitral valve disease. Urgent surgery for excision of the LA mass with the atrial septum and reconstruction by autologous pericardial patch was performed. There was no pathological change in the mitral valve. Due to surgical injury to the conduction system, implantation of a permanent pacemaker was required postoperatively. Histopathological examination revealed calcification, fibrosis, and thrombus formation. LA thrombus without any history of mitral valve disease or atrial fibrillation is rare. Although the mechanism of the present case was unclear, extensive calcified LA myxoma or undiagnosed patent foramen ovale might have been associated with the disease. .

Pulmonary vein obstruction after catheter ablation in a patient with partial anomalous pulmonary vein connection.

A 75-year-old man with symptomatic atrial fibrillation was referred to our hospital for catheter ablation. Preprocedural echocardiogram showed mild-moderate degree mitral regurgitation (MR) and mild tricuspid regurgitation (TR) with transvalvular peak gradient (TVPG) of 27 mmHg. The complete isolation of the pulmonary veins was performed by radiofrequency ablation, and the patient was kept in sinus rhythm after the procedure. However, the exertional dyspnea had gradually developed one year after the procedure. Echocardiogram showed severe TR with TVPG 60 mmHg. MDCT showed partial anomalous pulmonary vein connection (PAPVC) of the left upper pulmonary vein and the occlusion of left lower pulmonary vein ostium: pulmonary venous flow of the left upper lung was drained into the brachiocephalic vein. The patient underwent surgical correction of PAPVC and annuloplasty of the mitral and tricuspid valve. Although it is unclear whether there is direct causal relationship between PAPVC and PV obstruction, anatomical evaluation of PVs is important in patients undergoing catheter ablation. .

[Predictors of chronic aortic events associated with uncomplicated type B aortic dissection].

OBJECTIVE: Stent-graft repair may emerge as a first-line therapy for acute complicated type B dissection(C-TBD), while debate continues over thoracic endovascular aortic repair (TEVAR) for uncomplicated type B aortic dissection (U-TBD). Aggressive medical therapy, which confers a 1-year survival rate of 80-90%, is deemed appropriate for most of these patients. However, it is reported that aortic complications occur in ≤ 50% patients within 5 years after surgery. Subgroups of patients with U-TBD may benefit from early stent-graft placement, but identification of these patients remains difficult. Therefore, we assessed the predictors of chronic aortic events associated with U-TBD. METHODS: Between January 2001 and April 2012, 49 patients diagnosed with communicating U-TBD without aneurysm formation were admitted to our hospital. These patients were divided into 2 groups:group AC (n=25) with chronic aortic complications (aneurysm formation, aortic diameter expansion of 5 mm/0.5 year, re-dissection, and rupture) and group NC (n=24)with no aortic complications. We assessed and compared patient profiles and imaging findings between the 2 groups. RESULTS: Aortic diameter ≥ 40 mm was more often seen in group AC than in group NC (p=0.018). In addition, intimal tear in the distal arch was more often seen in group AC than in group NC ( p=0.002). Initial aortic diameter was significantly larger in group AC than in group NC (p=0.004). There was no significant difference in the length of communicating false lumen between the 2 groups ( p=0.107). CONCLUSIONS: Early endovascular intervention may be appropriate for U-TBD in cases displaying an initial aortic diameter ≥ 40 mm and an initial tear in the distal arch. It is expected that randomized studies, including ADSOAB study (a study on the efficacy of endovascular grafting in uncomplicated acute dissection of the descending aorta.), will resolve the limitations of our retrospective study.

Initiation factor 2, tRNA, and 50S subunits cooperatively stabilize mRNAs on the ribosome during initiation.

Initiation factor 2 (IF2) is a key factor in initiation of bacterial protein synthesis. It recruits initiator tRNA to the small ribosomal subunit and facilitates joining of the large ribosomal subunit. Using reconstituted translation system of Escherichia coli and optical tweezers, we directly measure the rupture force between single ribosomal complexes and mRNAs for initiation complexes in the presence and the absence of IF2. We demonstrate that IF2 together with codon recognition by initiator tRNA increases the force required to dislocate mRNA from the ribosome complexes; mRNA stabilization by IF2 required the presence of a joined 50S subunit, and was independent of bound guanine nucleotide. IF2 thus helps lock the 70S ribosome over the start codon during initiation, thus maintaining reading frame. Our results show how mRNA is progressively stabilized on the ribosome through distinct steps of initiation.