Literature search

Our search strategy produced a total number of 587 records, which were reduced to 275 articles after removal of duplicated studies. Following full-text screening, 13 studies satisfied our inclusion criteria and were identified for inclusion in our study [10,11,12,13,14,15,16,17, 19, 28,29,30,31]. Details are provided in PRISMA flowchart, Fig. 1.

Fig. 1Characteristics of included studies

Thirteen studies were included in our systematic review and meta-analysis, with a total of 5541 patients in horizontal aorta group and 7692 patients in the non-horizontal aorta group. All of the included studies were observational studies, and most of the studies were conducted in the United States (40%) and Turkey (20%). The mean age of patients in the horizontal aorta group was 83.2 ± 7.5 and 82.1 ± 8.1 in the non-horizontal aorta group.

Risk-of-bias assessment

Newcastle–Ottawa scale determined that all the included studies pose low risk of bias. Detailed ROB is provided in Supplementary Table 2.

Outcomes of TAVR in horizontal versus non-horizontal aortaShort-term (30-day) mortality

The meta-analysis included 12,285 patients. The overall risk ratio favored the non-horizontal aorta group (RR = 0.76; 95% CI [0.62–0.95], P = 0.01). Pooled studies demonstrated no heterogeneity (I2 = 0%; P = 0.67). Analysis based on the type of valve used favored the non-horizontal aorta in the SEV subgroup (RR = 0.68; 95% CI [0.54–0.87], P < 0.01) (I2 = 0%; P = 0.69). The overall risk ratio did not favor the horizontal or non-horizontal aorta in the BEV subgroup (RR = 1.13; 95% CI [0.50–2.56], P = 0.76) (I2 = 0%; P = 0.60) (Fig. 2). On performing subgroup analysis based on valve generation, we did not find any difference between non-horizontal and horizontal groups on using Corevalve (RR = 0.77; 95% CI [0.58–1.02], P = 0.07) (I2 = 0%; P = 0.36), but the use of Evolut R favored the non-horizontal group (RR = 0.48; 95% CI [0.24–0.97], P = 0.04) (I2 = 0%; P = 0.86) (Fig. S1).

Fig. 2

Short-term (30-day) mortality forestplot

One-year mortality

The meta-analysis included 443 patients. The overall risk ratio did not favor either of both groups (RR = 0.68; 95% CI [0.38–1.22], P = 0.19). Pooled studies demonstrated no heterogeneity (I2 = 0%; P = 0.84) Fig. 3.

Fig. 3

One-year mortality forestplot

Stroke

The meta-analysis included 12,110 patients. The overall risk ratio did not favor any aortic angulation (RR = 0.85; 95% CI [0.68–1.05], P = 0.13). Pooled studies were homogenous (I2 = 0%; P = 0.67). There was no difference between the horizontal and non-horizontal groups with BEVs (RR = 0.59; 95% CI [0.21–1.61], P = 0.30) (I2 = 10%; P = 0.33) and with SEVs (RR = 0.86; 95% CI [0.67–1.11], P = 0.24) (I2 = 4%; P = 0.40) (Fig. 4). On subgroup analysis according to valve generation, we did not find any difference between both anatomical groups when using Corevalve (RR = 0.9; 95% CI [0.66–1.24], P = 0.53) (I2 = 0%; P = 0.46), or Evolut R (RR = 1.19; 95% CI [0.36–3.89], P = 0.77) (I2 = 0%; P = 0.46) (Fig. S2).

Fig. 4Myocardial infarction (MI)

The meta-analysis included 5537 patients. The overall frequency of MI was similar with both a horizontal and non-horizontal aorta (RR = 0.79; 95% CI [0.38–1.64], P = 0.52), with no statistical difference between horizontal and non-horizontal aorta with using BEVs or SEVs (RR = 0.47; 95% CI [0.06–3.75], P = 0.48) (I2 = 0%; P = 0.77) and (RR = 0.71; 95% CI [0.30–1.70], P = 0.44) (I2 = 0%; P = 0.87), respectively. Pooled studies were homogenous (I2 = 0%; P = 0.96) (Fig. 5).

Fig. 5

Myocardial infarction forestplot

Major or life-threatening bleeding

The meta-analysis included 3,326 patients. The overall risk ratio did not favor a non-horizontal aorta (RR = 0.81; 95% CI [0.62–1.07], P = 0.14). Pooled studies were homogenous (I2 = 0%; P = 0.82) (Fig. 6).

Fig. 6

Major or life-threatening bleeding forestplot

New permanent pacemaker implantation (PPI)

The meta-analysis included 12,156 patients. The overall risk of PPI rates was lower with a non-horizontal aorta (RR = 0.87; 95% CI [0.79–0.94], P < 0.01). PPI rates were also lower in the non-horizontal group with both BEVs and SEVs (RR = 0.67; 95% CI [0.47–0.96], P = 0.03) (I2 = 8%; P = 0.35) and (RR = 0.88; 95% CI [0.80–0.97], P < 0.01) (I2 = 0%; P = 0.92), respectively (Fig. S3). Pooled studies did not display heterogeneity (I2 = 0%; P = 0.89). On subgroup analysis, we found no difference between both anatomical groups when using both Corevalve (RR = 0.89; 95% CI [0.72–1.11], P = 0.31) (I2 = 14%; P = 0.28), and Evolut R (RR = 0.81; 95% CI [0.48–1.38], P = 0.45) (I2 = 0%; P = 0.74) (Fig. S4).

Moderate or severe aortic regurgitation (AR)

The meta-analysis included 8433 patients. The overall risk of AR did not favor either a horizontal or non-horizontal aorta (RR = 0.99; 95% CI [0.75–1.30], P = 0.93). Pooled studies showed non-significant heterogeneity (I2 = 21%; P = 0.26), and also there was no difference between horizontal and non-horizontal aorta with the use of BEVs or SEVs (RR = 1.12; 95% CI [0.44–2.85], P = 0.81) (I2 = 0%; P = 0.46) and (RR = 0.89; 95% CI [0.71–1.13], P = 0.34) (I2 = 0%; P = 0.47), respectively (Fig. S5).

Moderate or severe paravalvular leak (PVL)

The meta-analysis included 4096 patients. The overall risk of significant PVL favored the non-horizontal aorta group (RR = 0.70; 95% CI [0.55–0.90], P < 0.01). PVL was increased with a SEV in a horizontal aorta (RR = 0.66; 95% CI [0.46–0.94], P = 0.02) (I2 = 0%; P = 0.45), but not with a BEV in a horizontal aorta (RR = 0.92; 95% CI [0.27–3.14], P = 0.89) (I2 = 0%; P = 0.84). Pooled studies demonstrated no heterogeneity (I2 = 0%; P = 0.76) (Fig. S6).

Left bundle branch block (LBBB)

The meta-analysis included only two studies with a total of 3112 patients. The overall risk of new LBBB was less in the non-horizontal aorta group (RR = 0.80; 95% CI [0.68–0.94], P < 0.01). Pooled studies were homogenous (I2 = 0%; P = 0.41) (Fig. S7).

Major vascular complications

The meta-analysis included 6904 patients. The overall risk ratio did not favor any group (RR = 0.89; 95% CI [0.69–1.13], P = 0.33). Pooled studies demonstrated no heterogeneity (I2 = 0%; P = 0.65) (Fig. S8). When performing subgroup analysis based on valve generation, we did not find any difference between both anatomical groups on using Corevalve (RR = 0.8; 95% CI [0.62–1.03], P = 0.08) (I2 = 0%; P = 0.49), or Evolut R (RR = 0.7; 95% CI [0.34–1.46], P = 0.34) (I2 = 0%; P = 0.95) (Fig. S9).

Acute kidney injury (AKI)

The meta-analysis included 10,802 patients. The overall risk ratio did not favor any group (RR = 0.97; 95% CI [0.74–1.27], P = 0.82). It also did not favor any group with BEVs (RR = 1.76; 95% CI [0.62–4.97], P = 0.29) (I2 = 0%; P = 0.82) or SEVs (RR = 0.81; 95% CI [0.64–1.02], P = 0.07) (I2 = 0%; P = 0.56). Pooled studies displayed non-significant heterogeneity (I2 = 19%; P = 0.26) (Fig. S10). Subgroup analysis based on valve generation revealed no difference between both non-horizontal and horizontal groups with the use of Corevalve (RR = 0.96; 95% CI [0.78–1.18], P = 0.69) (I2 = 0%; P = 0.9), or Evolut R (RR = 0.83; 95% CI [0.31–2.18], P = 0.7) (I2 = 0%; P = 0.7) (Fig. S11).

Annular rupture

Only two studies with a total of 4309 patients reported the incidence of annular rupture. The overall risk ratio did not favor either of the two groups (RR = 0.47, [95% CI 0.13–1.74], P = 0.26). The pooled studies showed no heterogeneity (I2 = 0%, P = 0.67) (Fig. S12).

Valve embolization

The meta-analysis included 9908 patients. The overall risk ratio did not favor any anatomical group (RR = 0.82; 95% CI [0.60–1.13], P = 0.22). Also there was no difference between both anatomical groups with using BEVs (RR = 0.77; 95% CI [0.11–5.41], P = 0.79) (I2 = 0%; P = 0.82) or SEVs (RR = 0.85; 95% CI [0.60–1.19], P = 0.34) (I2 = 9%; P = 0.36). Pooled studies were homogenous (I2 = 0%; P = 0.78) (Fig. S13).

Cardiac tamponade

The meta-analysis included 1,598 patients. The overall risk ratio did not favor either aortic groups (RR = 1.10; 95% CI [0.47–2.59], P = 0.83). Pooled studies were homogenous (I2 = 0%; P = 0.90) (Fig. S14).

Coronary obstruction

The meta-analysis included 5273 patients. The overall risk ratio did not favor either aortic groups (RR = 0.94; 95% CI [0.37–2.37], P = 0.90). Pooled studies displayed no heterogeneity (I2 = 0%; P = 0.88) (Fig. S15).

Need for second valve

The meta-analysis included 5508 patients. The overall risk ratio significantly favored the non-horizontal aorta group (RR = 0.62; 95% CI [0.42–0.91], P = 0.02) and significantly favored the non-horizontal aorta group in the SEV subgroup (RR = 0.50; 95% CI [0.26–0.93], P = 0.03) (I2 = 26%; P = 0.26), but did not favor either aortic angulation groups in the BEV subgroup (RR = 0.89; 95% CI [0.26–3.04], P = 0.85) (I2 = 0%; P = 0.77). Pooled studies did not demonstrate heterogeneity (I2 = 0%; P = 0.60) (Fig. S16).

Total contrast used, mL

The meta-analysis included 8478 patients. The volume of contrast used was not affected by the degree of aortic angulation (MD = − 2.12; 95% CI [− 6.37 to 2.13], P = 0.33) and the overall effect size did not favor any group with using either BEV or SEV (MD = 2.23; 95% CI [− 2.77 to 7.24], P = 0.38) (I2 = 0%; P = 0.56) and (MD = − 5.48; 95% CI [− 12.06 to 1.09], P = 0.10) (I2 = 46%; P = 0.09), respectively. Pooled studies revealed significant heterogeneity (I2 = 49%; P = 0.02) (Fig. S17).

Total fluoroscopy time (minutes)

The meta-analysis included 6444 patients. The overall mean difference significantly favored the non-horizontal aorta group (MD = − 1.02; 95% CI [− 1.98 to − 0.07], P = 0.04). The overall effect size did not favor either group with using the BEV or the SEV subgroups (MD = − 0.12; 95% CI [− 1.15 to 0.92], P = 0.82) (I2 = 0%; P = 0.50) and (MD = − 1.54; 95% CI [− 3.75 to 0.66], P = 0.17) (I2 = 72%; P < 0.01), respectively. The pooled studies showed significant heterogeneity (I2 = 58%; P = 0.01) (Fig. S18).

Length of hospital-stay (days)

The meta-analysis included 1717 patients. The overall mean difference did not favor either aortic angulation groups (MD = − 0.67; 95% CI [− 1.58 to 0.24], P = 0.15). The pooled studies showed significant heterogeneity (I2 = 78%; P < 0.01) (Fig. S19).