Using a pheatmap in arrangeGrob

I'm attempting to plate two plots in the same .jpg using arrangeGrob(). I've only just started learning about grids and grobs and I think I know what the problem is: pheatmap is a grid object and containing grob objects, not allowing me to put it in arrangeGrob. Is this true?

Would I somehow need to put the qplot in a grid and the pheatmap in a grid and then put those grids in a new grid?

library(grid)
library(gridExtra)
library(pheatmap)
library(ggplot2)
hmdat=rbind(c(1,2,3),
            c(3,4,5),
            c(5,6,7))
hm=pheatmap(hmdat)
qp=qplot(1,1)
lm=rbind(c(1,2,2),
         c(1,2,2))
jpeg("plots.jpg")
arrangeGrob(qp,hm, layout_matrix=lm)
dev.off()

The above code snippet runs just fine when using

arrangeGrob(qp,qp, layout_matrix=lm)

I'm not sure if you wanted to have 6 figures or you wanted to have two figures one with twice as wide as the other one (I tried to do minimum code change):

library("grid")
library("gridExtra")
library("pheatmap")
library("ggplot2")

hmdat=rbind(c(1,2,3),
            c(3,4,5),
            c(5,6,7))

hm <- pheatmap::pheatmap(hmdat)
qp <- qplot(1,1)

lm <- rbind(c(1,2,2),
         c(1,2,2))
grid.arrange(grobs = list(qp,hm[[4]]), layout_matrix = lm)

which will give you:

The same way you can have multiple pheatmaps side-by-side:

library("grid")
library("gridExtra")
library("pheatmap")

hmdat <- rbind(c(1,2,3),
            c(3,4,5),
            c(5,6,7))

hm <- pheatmap::pheatmap(hmdat)

lm <- rbind(c(1,2),
         c(3,3))
grid.arrange(grobs = list(hm[[4]],
                          hm[[4]],
                          hm[[4]]),
             layout_matrix = lm)

As @hrbrmstr mentioned in the comment, you should use the 4th item in the pheatmap object. Also remember to provide grobs as list to the grid.arrange